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expressed in British thermal units radiated per square foot per hour as 16×10-(T ̧*-T,*), where T, and T, are the temperatures of the incandescent gases and of the boundary respectively in degrees Fahrenheit absolute. This formula may be applied in order to find a theoretical upper limit to the quantity of heat radiated to the firebox boundary on the assumption that the flame is actually composed of solid masses of incandescent carbon, and so follows Stefan's law. Thus, with flame and boundary temperatures respectively of 3000° and Soo° F. absolute, the heat radiation is 129,600 British thermal units per square foot per hour. With temperatures respectively of 4000 and 800° the radiation amounts to 410,000 British thermal units, showing the rapidity of increase of radiation as the flame temperature rises. Stefan's law does not apply to cases where the gases are not incandescent.

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In transmission by conduction and convection the heatflow path from the interior of the mass of gas in the firebox to a point in the interior of the mass of water is made up of the following parts:-the gaseous part from the starting point to the gas film clinging to the plate; the gas film itself; the surface of contact between the plate and the gas; the metallic plate; the surface of contact between the plate and the water; the water film; the water from the film to the point in the mass of water. To these must be added, for dirty plates, a layer of sooty deposit on the gas side and a layer of scale on the water side, on which there may also be a deposit of oily matter. There is evidence that 98 per cent. of the total " temperature head is required in order to force the heat from the gas into the plate, the remaining 2 per cent. alone being required to transfer the heat from the plate to the water in the boiler. The presence of oily matter may raise the temperature difference between the hot side of the plate and the water from 68° F. to 550° F., depending on the nature and thickness of the greasy deposit. The thickness of the film of gas clinging to the plate is probably of the order of 1/40-inch, and accounts for the greater part of the resistance offered to heat transmission by the total path of flow. The water film clinging to the plate also contributes to the resistance, as convection currents cannot exist in it, and heat must be transferred across it by the conductivity of the water forming the film, which is known to be exceedingly small.

If these films be completely or partially destroyed, the head required to effect the heat transmission from the gas to the water across the plate will be considerably reduced. One of the most potent factors in disturbing the gas film is the velocity possessed by the moving gases. Most of the work in connection with heat transmission since the time of Rankine shows attempts to introduce a velocity factor variable into the expressions. Again, owing to the temperature gradient from the centre of the flue gases to the boundary, the efficiency must increase with a decrease in the size of the flue within limits. Hence the hydraulic mean depth of the flue must form a factor. The importance of good water circulation lies in the fact that forcing water across the heating surface with a high velocity has the effect of breaking up the water film.

Notwithstanding the large number of researches bearing on the subject of heat transmission. there is a general absence of complete data regarding the actual phenomena occurring in a steam boiler when working under ordinary conditions of practice. For instance, no data exist which gives the temperature gradients at different parts of a boiler flue with accuracy. Researches have had little effect in modifying the general design of steam boilers, although the costly nature of these may be understood from a set recently made by the United States Geological Survey, costing 100,000 dollars. The author suggests that the institution might undertake a research in which steam boilers of different types under practical conditions may have all the elements of their working measured, together with temperature measurements for the purpose of establishing the temperature gradients at different parts of the heating surface. Such a research would be costly, but would be well worthy of the institution.

The paper contains elaborate indexes giving reference to all known work bearing on the subject; these will be extremely valuable to all interested in heat transmission.

THE ANTIQUITY OF MAN IN SOUTH
AMERICA.

THE views held by Dr. Florentino Ameghino as to the antiquity of man in South America are based on the occurrence of split bones, and bones showing signs of having been cut, side by side with certain scoriaceous products, the "tierras cocidas" of Argentina. We are not as yet in possession of figures of the bones, and it may be presumed that they are regarded as of less importance than the baked and reddened earths. A lively controversy has arisen round the latter, and the question appears to be one that must be decided by the geologist rather than by the anthropologist.

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Several series of deposits of Cainozoic age are recog nised along the curving coast-line south of the mouth of the Rio de la Plata, past Mar del Plata, and away towards Bahia Blanca. The orientation of one of Dr. Ameghino's maps is unsatisfactory; but much topographical and descriptive matter will be found in his paper "Las formaciones sedimentarias de la región litoral de Mar del Plata y Chapalmalán (Anales del Museo nacional de Buenos Aires, tomo xvii., p. 343; published November 28, 1908). This, so far as the baked earths are concerned, is overshadowed by a memoir by Señor Outes, Dr. Ducloux, and Dr. H. Bücking, of Strassburg, issued on September 15 of the same year ("Estudio de las supuestas escorias y tierras cocidas de la serie pampeana de la República Argentina," Revista del Museo de la Plata, tomo xv., p. 138).

The two authors who have called in Dr. Bücking to their assistance review the question historically. The Araucanian formation, with the Monte Hermoso beds, which Florentino Ameghino prefers to regard as Miocene, is very generally placed by other authors in the Pliocene; but this does not affect the arguments of Outes and Ducloux. They point out that in 1865 Heusser and Claraz, in a paper published in French at Zürich, recognised cellular, and apparently volcanic, material in the lower part of the Pampas beds near Mar del Plata. More than twenty years later, in 1887, Florentino Ameghino gathered similar "'escorias at Monte Hermoso, 60 km. north-east of Bahia Blanca, and in 1889 described others from the neighbourhood of La Plata. These places are, of course, all remote from any volcanic vents that have so far been discovered.

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Meanwhile, from 1874 onwards, the more obscure materials known as tierras cocidas were collected by Señores Juan, Carlos, and Florentino Ameghino from various places in the province of Buenos Aires, and the last-named writer claimed them as traces of ancient hearths, and as indicating man's antiquity in South America. The field was widened by other observers, and the typical specimens, with new ones personally collected, have now been investigated by Outes and Ducloux.

These authors make no claim to originality in rejecting the opinion of Florentino Ameghino. They quote the views of Steinmann in 1906 (p. 160 of their memoir) as to the andesitic nature of the scoriæ and baked earths, and they go back (p. 191) to Charles Darwin, who recorded, in 1851, the occurrence of pebbles of pumice on the surface of the raised terrace at Monte Hermoso. Darwin attributed these pebbles to the transporting action of ancient rivers, and pointed out how the rivers Negro and Chupat bring down volcanic pumice and scoriæ at the present day. Outes shows that such materials need not have been carried directly from the Andes, but may have been washed out of the detrital volcanic beds of the Araucanian formation, which is much older than the Fampas beds, and possibly than those of Monte Hermoso. The inclusion of vegetable remains in the scoriæ is held not to militate against their volcanic origin. Doering has urged the importance of laterisation in determining the characters of the red beds in the Lower Pampas series. and Outes (p. 194) quotes his views with approval as explaining many of the "baked earths." The elaborate chemical work of Ducloux (pp. 162-184) goes to show that the loess of the Pampas beds and the included scorie and "baked earths" have a similar chemical composition, and masses like volcanic scoriæ have been made artificially

by heating the loess at 1300° C. to 1350° C. The loess appears to contain abundant minerals that characterise volcanic lavas. The analyses given show a silica percentage of about 66 for the debatable scoriæ and "baked earths," and of only some 57 for the specimens of loess; but the latter loses some 13 per cent. of water, against 4 or 5 per cent. from the former materials. Ducloux opposes the suggestion of Ameghino that alkalies from the associated vegetation, burnt up with the loess, have entered into the composition of the scoriaceous matter.

H. Bücking's petrographic contribution (p. 185) should certainly have been illustrated. The writer, after microscopic examination, has no hesitation in classing the scoriæ as ordinary andesites. He traces volcanic lapilli in a baked earth" from " Chapadmalal," and describes features in this material and in others sent to him which suggest a laterisation of volcanic dust.

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Dr. Ameghino's paper, published in November, 1908, is largely stratigraphical. The beds of Monte Hermoso (p. 344) are here held to be much older than the Pampas formation, on account of their absolutely distinct fauna. If, then, man or his precursor" is responsible for the baked earths" found among them, the human race in South America may be traced back further than even Ameghino had previously supposed. We gather that this paper was well advanced before the issue of that by Outes and Ducloux, for Ameghino has since found it necessary to emphasise still further his views on the "baked earths" in a specially written memoir, in both French and Spanish, entitled "Productos piricos de origen antrópico en las formaciones neogenas de la República Argentina (Anales del Museo nac. de Buenos Aires, tomo xix., p. 1; published February 17). He points out that the analyses of Ducloux merely show that the alleged volcanic cinders might have been formed from the fusion of the earth in which they lie, which is precisely the point that Ameghino wishes to establish. But it is not clear that the fused products (p. 17), prepared by Ameghino himself at 950° to 1000° C., have been submitted to microscopic examination, or that they exhibit the felspars and other associated minerals found by Bücking in the scoriæ.

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Ameghino (p. 19) states that certain burrows formed as nests by the bee Ancyloscelis analis occur in the "baked earth," which must therefore have been burnt after the formation of the nests. Presumably this bee must also be transferred to the Miocene period if this argument is to be sustained. The paper concludes with a statement of how Outes and Ducloux failed to bring forward at Santiago, in Chile, a promised refutation of Ameghino's reiterated views. We may be happy, perhaps, if they consider that enough has now been said. While Florentino Ameghino does not seem to appreciate sufficiently the changes induced in rocks by laterisation, his critics have certainly not utilised to the full the resources of modern petrology. Probably some independent worker will ultimately arrive upon the scene, and we venture to think that he will confirm the views of Steinmann, Outes, and Ducloux. The widely distributed materials which have aroused so much discussion are hardly likely to add to our knowledge of the antiquity of man in South America. G. A. J. C.

AGRICULTURE AT THE BRITISH
ASSOCIATION.

IN view of the outstanding importance of agriculture in Manitoba, it was decided to concentrate attention on a few of the fundamental problems of the North-west and to discuss them as fully as possible both in the subsection itself and in joint meetings with other sections. Such joint discussions are particularly valuable, because the problems in agricultural science are highly complex, and have generally to be dealt with by men working away from large university centres and only occasionally coming into contact with pure men of science. Only those who have had to work under such conditions know what it means to attempt research work in small laboratories in the country without the stimulus of the research atmosphere, often, indeed, with the drag of a considerable amount of routine work and little opportunity of discussing the

problem with the chemist or botanist who could throw much light upon it. Under present conditions almost the only opportunity the agriculturist has of meeting his fellowworkers in the region of pure science is at the British Association meeting. For this reason agriculturists are awaiting with no small interest the outcome of the proposal made last year, and carried forward another stage this year, that agricultural science shall form a definite and permanent part of the British Association programme.

In his presidential address Major Craigie dealt with the future wheat supply of the world, and showed that there was no reason for the gloomy apprehensions that have at times been raised, and particularly by Sir W. Crookes at Bristol in 1898, as to whether or not population would outstrip wheat production. The address is printed in extenso in NATURE (September 30).

Dr. W. Saunders gave an account of the experimental farm system in Canada. The central farm is at Ottawa, where the scientific staff reside. There are eight subsidiary stations situated at various points between the Atlantic and Pacific coasts, viz. at Prince Edward Island, Nova Scotia, Branden (Man.), Indian Head and Rosthern (Sask.), Lacombe and Lethbridge (Alta.), Agassiz (B.C.). At each of these a scheme of experiments drawn up at Ottawa is carried out under the supervision of an experienced superintendent; different varieties of crops suited to the district and different methods of management are all investigated, and the results published as widely as possible. Any abnormalities or matters of general interest that may require further elucidation are examined in greater detail at Ottawa.

The possibility of extending the food production of Canada was discussed at a joint meeting with the Economics Section, papers by Prof. Brigham, secretary of the Association of American Geographers, and Prof. Mavor, of the Toronto University, forming the text. The possible wheat area of the three provinces Manitoba, Alberta, and Saskatchewan has been put at 17 million acres, and the possible output at 317 million bushels, which estimates are not at all accepted by the optimistic westerners. Prof. Mavor, however, points out that wheat cultivation cannot continue to be the mainstay of husbandry, but that mixed farming must become more common. Already, indeed, the wheat area is going down in Ontario, and in certain other districts it is not increasing so rapidly as the area under oats. Dry farming, which alone could be practised over large areas, is as yet on its trial. The difficulty of forming satisfactory estimates is complicated by the fact that two sets of mutually inconsistent statistics are officially issued, one compiled by the Dominion Statistical Department, the other by the provincial authorities.

A joint meeting with the botanical and chemical sections was held for the discussion of wheat problems. An important contribution to the history of the various wheats was made by Dr. Stapf, whose paper was read in his absence by Colonel Prain. Hitherto this question has been very obscure, and has formed the subject of much speculation. Dr. Stapf has succeeded in applying more precise methods, and in replacing the vague ideas hitherto held by definitely ascertained facts. The factors determining the yield of wheat formed the subject of a paper by Messrs. A. D. Hall and E. J. Russell. Wheat is very dependent on a supply of nitrogenous food-stuff; indeed, for small increments of nitrogen a more than proportional crop return is obtained. At a later stage the returns diminish, and after a time cease to yield any profit. Phosphates are of less direct importance, but have considerable indirect effect; in particular, they often enable the crop to be harvested at a somewhat earlier date, and thus they tend to extend further northwards the region of profitable production. It was also shown that wheat is capable of withstanding drought conditions, and is therefore a crop adapted to dry regions. Mr. F. T. Shutt discussed the influence of environment on the composition of the grain. Whilst not prepared to maintain that the percentage of nitrogen, phosphoric acid, or potash in the soil would appreciably affect the percentage of these substances in the grain, he nevertheless showed that the composition of the grain was influenced by its surroundings. Soil moisture affects the quantity of nitrogen present; on

adjacent pieces of ground with varying amounts of organic matter, and therefore of moisture, the nitrogen was found to decrease with increasing water content. Thus a strong wheat containing 12.5 per cent. of nitrogen yielded on newly broken prairie land a grain containing only 9.9 per cent. of nitrogen, but on adjacent older and drier land the grain contained 12-4 per cent. of nitrogen. Mr. Shutt's view is that the character of the gluten is a matter of heredity, whilst its amount depends on environ

ment.

Two papers then followed on the strength of wheat, one, by Mr. A. E. Humphries, in which strength was described from the miller's point of view, and one by Dr. E. F. Armstrong, in which the present position of the chemistry of wheat strength was set out. Good quality is the sum of excellence in several directions. The capacity for making large, shapely, and therefore well-aërated loaves; the facility with which large masses of dough can be handled in the bakehouse; the percentage of water required to make a dough of standard consistency, are all taken into account by the miller in valuing his flour. This paper of Mr. Humphries is of great value to the chemist in that it sets forth with clearness the problem that has to be solved; correlations are now wanted between the chemical composition of the flour and these various characters. Dr. Armstrong, in a critical review which was much appreciated, showed what had been done up to the present in tracing such connections, and set forth the methods by which it is possible in particular cases to judge the value of flour. No one chemical characteristic is sufficient; account must be taken of various factors, such as the percentage of nitrogen, the size of the starch grains, and others. Prof. Harcourt then described experiments he had conducted on the baking qualities of certain flours from the western provinces. When Alberta red flour was mixed with soft Ontario winter wheat, a distinctly better result was obtained than when either flour was baked alone. The value of these flours for blending purposes was thus demonstrated. Mr. W. B. Hardy then described the experiments he had made with Prof. Wood to emphasise the importance of mineral constituents of the flour on the plasticity of the gluten.

Dr. C. Saunders approached the subject from quite a different point of view, and described his experiments in breeding wheats. It is fortunately recognised in Canada that wheat may have to be bred to suit local requirements, and indeed has to be bred if the area of the crop is to be pushed northwards. Early ripening is essential in districts where the harvest may be spoiled by frost, and early ripening varieties are being produced by Dr. Saunders at Ottawa. A note on selection was then read by Prof. L. S. Klinck, of the Macdonald College. Finally, Prof. Zavitz discussed the influence of good seed as a factor in wheat production, and described also the work done at Guelph on selection and breeding. Altogether, the wheat papers formed a valuable summary of our knowledge of the various phases of the wheat problem, and general satisfaction was felt at the decision to print them in extenso and to issue them in the form of a pamphlet.

Another session was devoted to the discussion of forestry problems. Prof. Somerville opened by a paper on the outlook for timber supplies, pointing out that the consumption of timber is rising faster than the supply, the growing scarcity of timber being clearly reflected in its rising prices. During the past twenty-two years, nine out of thirty-two varieties examined had risen more than 100 per cent. in price, and only two had risen less than 25 per cent. It is to the interest of every country to take energetic steps to prevent waste of timber and to plant up such lands as are not otherwise wanted. The Canadian chief forester, Mr. R. H. Campbell, followed with a paper from which it appeared that perhaps Canada is not yet fully alive to the importance of the problem. The area of forest land is probably not more than 500-600 million acres, only half of which appears to be of actual value. Suggestions were made for conserving the supply, and various administrative, educational, and legislative reforms were urged. The entomological problem was next discussed by Messrs. Lockhead and Swaine, of the Macdonald Agricultural College, who showed that much remains to be done by

way of survey to ascertain the damage caused by forest insects. Mr.

A morning was devoted to live-stock problems. P. A. Mørkeberg, the Danish State expert on the breeding of dairy cattle, described the remarkable cooperative system obtaining in Denmark and its effect in increasing both the output and also the value of the output from the farms. Mr. Mørkeberg came over as the foreign representative of the subsection, and his paper was of great value by reason of its suggestiveness to the Canadian authorities who were present, and who are faced by a not dissimilar problem. Mr. Rutherford, the veterinary inspector at Ottawa, sketched out the general character of the western cattle trade, and Prof. Somerville described, his experiments at Cockle Park, in which a clay pasture has been improved by basic slag. Prof. Wilson, of Dublin, gave the results of his investigations into the history of the Aberdeen-Angus breed of cattle. The idea underlying the method is that an invading race would bring their cattle with them; thus the original cattle were black; the Romans brought white cattle; the Anglo-Saxons brought red; the Norsemen brought a hornless race: while a large flecked race was imported from Holland in the Seventeenth and eighteenth centuries. Prof. Wilson examines the history of each district, and shows how the local cattle have been derived.

The last meeting of the session was devoted to soil problems. Mr. F. T. Shutt described the prairie soils as characterised by a high percentage of organic matter, intimately mingled with clay and sand. The percentage of organic matter is of the greatest importance in determining their fertility, because it so often happens that water is the factor limiting their productiveness. It is hoped that this paper, which summarises a considerable amount of work on the subject, may soon be available for the agricultural chemist. Prof. Alway followed by studies on semi-arid and arid soils, where the problem is quite different in type from that on humid soils. It was found, for instance, that a crop of clover did not increase the succeeding wheat crop, because the clover had taken too much water from the soil. A mere determination of soil moisture is not sufficient to give useful data; the hygroscopic coefficient is wanted before the result can be interpreted. Prof. King, of Wisconsin, sent an admirable summary of his work on soil moisture, which will be much appreciated by English students. The phenomena connected with the water relationships of soils were dealt with in some detail, and a very useful warning was given with regard to dry farming.' By applying certain methods of cultivation that produce a firm subsoil and a loose surface soil it is possible to economise the water supply, and therefore to raise crops in arid or semi-arid regions normally almost desert land; but Prof. King points out that the rainfall goes more or less in cycles, and that the favourable results so often quoted have in some cases, at least, been obtained in seasons when there was quite a considerable amount of rain. Whilst fully admitting the close relationship between cultivation and soil moisture, of which, indeed, his own work forms the best illustration we have, he laid stress on the fact that the large-scale methods are in no sense fully developed.

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The last paper, by Messrs. A. D. Hall and E. J. Russell, dealt with the general problem of the conservation of soil fertility, especially with regard to the nitrogen of the soil. At least five factors affect the amount of nitrogen present. Two tend to increase it, viz. (a) bacteria fixing atmospheric nitrogen, and (b) the combined nitrogen brought down by the rain; and three to decrease it, viz. (c) drainage water. (d) bacterial action in decomposing organic matter, with liberation of free nitrogen, and (e) the growth of plants with its concomitant assimilation of nitrogen compounds. Three sets of cases were discussed. It was shown that the nitrogen content of land under arable cultivation declines when the produce is entirely removed and no organic matter is added as manure. When land rich in organic compounds is subjected to arable cultivation the destructive agents become very active, and the land loses nitrogen rapidly. On the other hand, when land is carrying natural vegetation which is not removed, there is a gain of nitrogen.

BOTANY AT THE BRITISH ASSOCIATION.

So far as Section K is concerned, the Winnipeg meeting must be pronounced to have been a distinct success. Though less than a dozen British botanists and only one Canadian were present, the numbers attending the section were about up to the average. This was largely due to the presence of a number of American botanists, many of whom communicated papers and in other ways contributed to the success of the meeting.

The opening address of the president, Lieut.-Colonel Prain, was delivered on Thursday, August 26. It dealt chiefly with the position of modern systematic botany, and its relations to palæobotany, phytogeography, and other branches of botanical study. The address was published in full in NATURE of September 30.

The papers read during the meeting may be roughly classified according to subjects.

Cytological and Fungal Papers.

Prof. J. B. Overton (of Wisconsin) contributed a paper on the organisation and reconstruction of the nuclei in the root-tips of Podophyllum peltatum. After summarising the work of Grégoire and others, the author described his own observations, which, in his opinion, strongly support the view of the individuality of the chromosomes. During the passage of the chromosomes from the equatorial plate to the poles, they exhibit progressive vacuolisation. Dr. Overton believes that each individual chromosome increases in size, and ultimately forms an independent elementary reticulum. Thus the reticulum of the resting nucleus is composed of a number of these smaller reticula. Conversely, during the earlier prophases of division, the chromosomes become more condensed and distinct, and, joining end to end, give rise to the well-known spireme.

Mr. Harold Wager communicated a paper by Miss A. Peniston and himself on the nucleus of the yeast plant. The authors contend that the so-called vacuole of the yeast cell is in reality part of the nuclear apparatus. This vacuole is surrounded by a peripheral chromatin network, which in its turn is connected with a stainable nucleolus. The paper was illustrated by a number of convincing drawings.

Miss H. C. I. Fraser discussed the nuclear phenomena of Ascomycetes in relation to heredity. Fertilisation in the Ascomycetes may be either normal or degenerate. The latter, which consists of the fusion in pairs of either ascogonial or even vegetative nuclei, is found in cases where one or both sexual organs are absent. Fertilisation of either type is followed by a second nuclear fusion in the ascus. The sexual fusion is compensated by a true meiotic reduction, while the fusion in the ascus is followed by a simpler brachymeiotic division. It thus appears possible to differentiate between sexual and asexual fusion by a study of the subsequent reduction phenomena.

Prof. A. H. R. Buller (of Winnipeg) gave an account of the production and dispersion of spores in the Hymenomycetes. A number of experiments were made on the rate of spore discharge, the path of the falling spores, &c. During the paper Prof. Buller gave a pretty demonstration of the discharge of spores from the fruit-body of a species of Polyporus. By suspending the fungus in a closed glass chamber, through which a concentrated beam of light was passed, the clouds of falling spores were rendered clearly visible. A full account of this work is contained in the book on fungal researches just published by the author.

Another paper by Prof. Buller, in collaboration with Mr. C. W. Lowe, dealt with the number of bacteria in the air of Winnipeg. Observations were made on the University campus every week for a year. Both the volumetric and the plate methods were employed. During the winter half of the year the average number of micro-organisms in ten litres of air was 0.9, while in the corresponding summer half the average number rose to 10-33.

Papers on Pteridophyta.

Prof. D. H. Campbell (Leland Stanford University) read a paper on the prothallium and embryo sporophyte of Danæa, a fine series of which (belonging to several species) had been procured in Jamaica. Of the points described by

the author, two may be mentioned. First, as compared with other Marattiaceæ, the ventral canal cell of the archegonium is very imperfectly developed. Secondly, no trace of a root can be found until the embryo has reached a considerable size. The first root then arises endogenously.

Prof. D. T. Gwynne-Vaughan communicated a paper by Dr. Kidston and himself on the ancestry of the Osmundaceæ. Lalesskya and Thamnopteris are two genera of primitive Osmundaceæ from the Permian deposits of Russia. The stem in these forms contains a protostele with a solid mass of xylem. The latter, however, is not homogeneous, as it consists of a central mass of short tracheids surrounded by a peripheral zone of normal scalariform tracheids. This central mass of short tracheids is held by the authors to be homologous with the parenchymatous pith of the modern Osmundaceæ. They also believe that the Osmundaceæ and Zygopterideæ have been derived from a common ancestor.

A paper was also presented by Mr. W. T. Gordon on the structure of a new Zygopteris. This species (Z. Pettycurensis) exhibits a protostele, a type of vascular system which had hitherto not been found in the group. This form thus occupies the same position in the Zygopterideæ as Thamnopteris schlechtendahlii does in the Osmundaceæ.

Ecological Papers.

Friday morning was largely devoted to the consideration of papers on ecology. The first was by Prof. H. C. Cowles, of Chicago, on the fundamental causes of succession among plant-associations. In dealing with the fact of succession, Prof. Cowles stated that plantassociations only exhibit this phenomenon when changes occur in the external conditions; but complete stability of conditions is rarely met with, so succession constitutes the normal course of events. The earlier stages may be termed the proximate, and the later ones the ultimate stages. Except in those cases where the proximate and ultimate formations are the same, as, for instance, in deserts, it is only in the ultimate stages that a plantassociation becomes relatively stable. The author then discussed a number of the causes of succession. Apart from such obvious ones as topographic and climatic changes, the most important are those which are more or less associated with the plants themselves. Of these, Dr. Cowles laid especial stress on two factors: the accumulation of humus, which involves changes in the temperature, and the moisture and air content of the soil; and the increase of shade, due to the increasing luxuriance of the vegetation. The ultimate formation of any upland will be composed of plants that can germinate in the densest shade that exists there. Other factors discussed were the invasion of an area by alien species, and the influence of man. The latter makes itself felt chiefly by reason of man's destructive activity. Speaking broadly, the effect of interference by man is to keep plant-associations more xerophytic than they would otherwise be.

Prof. F. Ramaley (Colorado) discussed the Rocky Mountain flora in relation to climate. He stated that the flora of the Rockies is remarkably uniform from Canada to Colorado; but any given species must be looked for at higher and higher altitudes as one travels southwards from Canada. The author is of opinion that the chief factor which determines this altitudinal distribution is temperature. This he regards as more important in this instance than either topography, soil, or rainfall.

Prof. B. E. Livingston (Baltimore) then gave an account

of the porous cup atmometer as an instrument for

ecological research. The author first emphasised the importance of evaporation determinations in ecological investigations, and then described the form of instrument he has himself used. Finally, he gave some useful hints with respect to precautions to be observed when using this instrument.

Prof. R. H. Yapp gave the result of some observations and experiments on the ecology of Spiraea Ulmaria. This plant exhibits curious seasonal changes in respect to the formation of glabrous and hairy leaves. It was shown that the production of these two types of leaves in nature varies with the annual march of evaporation and light intensity.

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Papers of Economic Interest.

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On Monday, August 30, there was a joint discussion on wheat " by the chemical, botanical, and agricultural sections. Most of the papers read at this discussion have already been noticed in NATURE (see the article Chemistry at the British Association, "" October 14, P. 475, and that on "Agriculture at the British Association in the present number). The only one that need be further dealt with here is an important botanical contribution by Dr. O. Stapf (communicated by Lieut.-Colonel Prain), on the history of the wheats.

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The wheats are generally divided into (a) the wheats proper, with tough spindles to the spikes, loose grains, and thick pericarps (N.B.-the first two of these characters are of economic importance, as they greatly facilitate threshing); (b) the spelt wheats, with brittle spindles, grains tightly enclosed in the husks, and thin pericarps. The former comprise the soft, hard, and English wheats, together with the dwarf and Polish wheats. The latter include the spelt wheats proper, the emmer and the einkorn wheats, and also the wild Triticum aegilopioides and T. dicoccoides.

After careful investigation, and in the light of recent discoveries, Dr. Stapf concludes that all the varieties of modern wheat may be traced to some four distinct primitive wild types: (1) the einkorn to Triticum aegilopioides, with its original home in Asia Minor and the Balkans; (2) the emmer and the hard wheats, as also the English and Polish, to Triticum dicoccoides, recently re-discovered by Mr. Aaronsohn in northern Palestine; (3) the spelt proper to Triticum cylindricum, in an area extending from Rumania to southern Russia; (4) the common or soft, and probably also the dwarf, wheats, to a still unknown species, which probably occurred either in Syria or Mesopotamia.

Dr. Stapf concluded his paper with an appeal for the systematic collection of all the wheats at present cultivated in the Old World, which must, he said, still include many of the more primitive races; also for a further exploration of the Orient, which might well result in the discovery of new wild forms.

Other papers of agricultural interest were read by Prof. H. Bolley (North Dakota), on the destruction of weeds in field crops by means of chemical sprays; and by Prof. Pammel (Iowa), on the delayed germination of seeds. The latter author experimented with the seeds of a number of species of weeds. He found that if the seeds were kept during the winter in paper packages, the percentage germination was lower, and the dormant period longer, than if the seeds were placed in sand and exposed to the climatic conditions of an ordinary winter.

On Thursday afternoon Mr. J. Parkin gave an interesting account of the industry of rubber cultivation. He referred to the various rubber-yielding trees, and more particularly to Hevea braziliensis, the Para rubber tree. After describing the introduction of the latter into the eastern tropics, Mr. Parkin dealt with the methods employed in tapping the rubber trees. He fully discussed the relation between the yield of rubber and the phenomenon known as 46 wound response, and also the nature of latex coagulation. The paper was fully illustrated with specimens of the plants, commercial rubber, the instruments used, &c. Mr. Parkin also demonstrated the actual coagulation of rubber latex.

Other Papers.

In contrast to the Dublin meeting, there was a noticeable dearth of physiological papers. One, however, was contributed by Prof. R. Willstätter, on the chemistry of chlorophyll. One of the points emphasised by this author was the essential difference between chlorophyll and hæmoglobin in respect to the metals bound up in their respective molecules. Iron occurs in that of hæmoglobin, while in the case of chlorophyll the iron is replaced by magnesium. The action of acids and alkalis on chlorophyll was also discussed.

Mr. J. Parkin put forward some rather novel views as to the evolution of the inflorescence. He is of opinion that racemose inflorescences have been in all cases derived from cymose. According to his view, solitary terminal flowers were primitive; these were succeeded by simple

dichasia, and these by compound dichasia. From the latter, racemose inflorescences may have been derived by an increase in the number of lateral flowers, with suppression of tertiary branching, and, finally, of the original terminal flower itself.

Miss E. J. Welsford described the life-history of Trichodiscus elegans, an alga belonging to the Chatophoraceæ. It was found in this species that various forms of reproduction may occur under identical external conditions. These results are somewhat at variance with the wellknown experiments of Klebs.

Dr. R. R. Gates (Chicago) discussed the effects of tropical conditions on the development of certain English Enotheras. Two species were grown from seed in a tropical greenhouse. The resulting plants were usually found to continue indefinitely in the rosette stage. Even when ordinary stems were produced they exhibited marked fasciation.

The Semi-popular Lecture.

This was given on the Friday afternoon by Mr. Harold Wager. He chose for his subject the perception of light in plants. The lecturer dealt with the problem as it affects both the lower, free-swimming organisms, such as Euglena, diatropic organs of the higher plants. With respect to the Chlamydomonas, &c., and also the various orthotropic and latter, Mr. Wager criticised Haberlandt's view of the agreeing that the optical behaviour of those cells may in ocellar function of the epidermal cells of leaves. While general be as Haberlandt suggests, the lecturer inclined to the view that the chlorophyll grains, rather than the cytoplasmic lining of the epidermal cells, constitute the thoroughly appreciated, was well illustrated by a number actual percipient organs. The lecture, which was of beautiful photographs.

Several botanical excursions were arranged during the meeting by the local secretary, Prof. Buller. One of these was to Hedingly, where a fine bit of uncultivated prairie was examined. Another was to Winnipeg Beach, on the shores of Lake Winnipeg. On a third occasion Elm Park, on the Red River, was visited. Some of the members of Section K also took part in the western excursion, and so had a further opportunity of witnessing some of the remarkable types of vegetation to be found in travelling from east to west across the North American continent.

UNIVERSITY AND EDUCATIONAL
INTELLIGENCE.

CAMBRIDGE. It is proposed that, in accordance with the recommendation contained in a report of the council of the Senate on the endowment of a professorship of German, the generous offer of Messrs. J. Henry Schröder and Company of the sum of 20,000l. for the endowment in the University of a professorship of German, to be known as the Schröder professorship of German, be gratefully accepted, and that the thanks of the University be conveyed to the donors.

The superintendent of the museum appointed Mr. C. L. Boulenger to the office of assistant of zoology has to the superintendent of the museum of zoology for one year from October 1, 1909. Mr. H. H. Thomas has been appointed curator of the botanical museum for a period of three years from Michaelmas, 1909, and Mr. Gordon Merriman has been appointed to the studentship in medical entomology lately held by Mr. F. P. Jepson.

The Vice-Chancellor, Mr. R. F. Scott, Mr. Fitzpatrick, Prof. Kenny, Dr. Anderson, Prof. Sorley, Sir J. J. Thomson, Mr. R. T. Wright, Mr. C. E. Grant, and Mr. H. McL. Innes have been nominated a syndicate to consider the question of providing pensions for professors and others in the service of the University.

LONDON. At the meeting of the Senate held on October 20, the degree of D.Sc. was granted to Mr. L. L. Fermor, an external student, for a thesis entitled "The Manganese Ore Deposits of India," and other contributions; and to Mr. S. Russ, an internal student, of University College, for a thesis on "The Active Deposits of Radio-active Sub

stances."

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