Prof.

form of graphite or simply intermixed carbon. Akerman holds that carbon exists in iron in three different forms which may be distinguished; other wellknown metallurgists confirm his views.

The following chapters, on iron versus steel for structural uses, and the stability of iron, are apparently ably written, and are recommended for the consideration of experts. The article on occlusion of gases in iron and steel is up to date. The researches of Graham, Deville, and Troost are quoted, and prominently those of Dr. Muller, to which latter the author appears to attach some importance. Iron, however, occludes other elements just as it does hydrogen-such as zinc, cadmium, magnesium, &c.; the same may be said even of carbon during the cementation process. Dr. Muller's method of collecting the gas by drilling gives no information as regards the gas actually occluded, which latter, it is evident, can only be extracted by heating in vacuum, as recommended by Prof. Roberts-Austen, and practised by Graham and Troost, also recently worked by Parry, Stead, and other chemists. JOHN PARRY.

THE THEORY OF LIGHT.

The argument given by Lord Rayleigh in his article in the "Encyclopædia Britannica," for showing that the effect of a wave is equivalent to half that of the first Huyghens zone, and that the phase of the disturbance is a quarter-period behind that from the pole, might with advantage have been given in greater fulness in Article 54 (the reference at the end of that article should be to Art. 154, Ex. 3).

The book is very complete so far as it goes, but the limits imposed by the author on himself do not allow him to show any very great originality in treating his subject, at least until we come to chapter ix., section iii., where he deals with the graphic method of solving problems in diffraction. In this section Cornu's beautiful method is employed, and many problems, usually only solved by analysis, are completely worked out by it.

The analytical solutions are, perhaps, a little hardly dealt with, as the methods of evaluating Fresnel's integrals given by himself, Gilbert, and Knochenhauer, only appear as examples. The theory of the diffraction gratings strikes us as being also rather brief. Rowland's concave gratings are best treated from the consideration that the waves from all the bright spaces arrive in the same phase. Possibly Bessel's functions are outside the limits

M1

R. PRESTON has written a valuable book on an important subject, one which will, as he hopes, be suited to the reading of junior students, and yet sufficiently full to meet the requirements of many who desire a more special acquaintance with the subject. At the same time it is difficult to avoid expressing the wish that he had carried the mathematical development of some parts of his subject a little further, and, if space required it, had omitted some of the more elementary details; though the work, within the limits laid down, is so well done, that criticism may seem ungenerous.

The historical method adopted in some parts of the book adds greatly to its interest, and the account given of the development of the subject, from the days of the Greek philosophers to the present time, will lead many to study the original sources of Mr. Preston's information with profit to themselves. It is a good thing for us to read how the first masters of the subject expressed themselves; to know what were the difficulties they felt, and what the problems which appeared important to their minds. We, who, thanks to Young and Fresnel, have had the difficulties that surrounded the wave theory in the time of Newton cleared away, are less apt than we might be at recognizing their magnitude, and at grasping the ingenuity and skill with which Newton treated the emission hypothesis, and the marvellous manner in which, in his hands, it was made to explain many of the phenomena of light.

In the earlier chapters of the book, after an explanation of the rectilinear propagation of light, a good deal of space is devoted to the explanation of phenomena usually dealt with under geometrical optics. The ordinary formulæ for prisms and lenses are deduced from the principle that the time from a point to its image is the same by all paths possible for the light-a principle which, in Lord Rayleigh's hands, has led to important results in the theory of optical instruments.

not, a reference to them would improve the treatment of the diffraction problems arising out of the case of a circular aperture.

Fresnel's theory of double refraction is given clearly in chapter xii., and the difficulties of finding a dynamical explanation of it are well stated. It is here, however, and in the chapter on the dynamical theory of reflection and refraction, that we think the limitation of the mathematical development unfortunate. The elementary theory of elastic solids is given sufficiently for optical purposes in several works accessible to students. The author might easily, if he had liked, have introduced a few pages of it in his own book. He would then have been able to give and discuss the theories of refraction and double refraction of both Green and Neumann, or McCullagh, and thus have added greatly to the value of the work.

The book is brought up to date in a satisfactory manner. The last chapter contains an account of the modern work on the electro-magnetic theory of light, including the recent experiments of Hertz.

ENGLISH PATENT LAW.

The Law and Practice of Letters Patent for Inventions; with the Patents Acts and Rules annotated, and the International Convention, a Full Collection of Statutes, Forms, and Precedents, and an Outline of Foreign and Colonial Patent Laws, &c. By Lewis Edmunds, D.Sc., (Lond.), F.C.S., F.G.S., of the Inner Temple, Esq., Barrister-at-Law; assisted by A. Wood Renton, M.A., LL.B., of Gray's Inn, Esq., Barrister-at-Law. (London: Stevens and Sons, Limited.)

pages, our readers may be disposed to think that the author must have achieved his purpose. On a closer inspection, however, the formidable proportions of the work become greatly diminished. We find that the actual text of the book is only some 425 pages, the remaining 515 pages being supplied by statutes, Patent rules, international regulations, voluminous forms, and an index. We have always understood that a legal text-book ought to be in form as concise, and we might almost say as condensed, as possible, consistently with the importance of the subject-matter. Mr. Edmunds does not appear, however, to pay much regard to this wholesome rule. We rarely remember to have seen a legal text-book more gratuitously padded out than the work now before us. To take one illustration, the author devotes nearly 200 pages to printing the Patent Acts 1883-1888, twice over, for what good purpose we are at a loss to understand. The notes which are appended to what we must, under the circumstances, call the first edition of the Patent Acts 1883-1888, are of considerable value, but we cannot approve the system of cross references, by means of which the author seeks to incorporate, under various sections of the Acts, passages from the preceding text. By this device, Mr. Edmunds seems to have attempted to combine in one volume two inconsistent methods of

text writing the method which constructs a book by noting the sections of an Act, and the method which, relegating the statutes to an appendix, makes the body of the text a continuous treatise. There is much to be said for each method. Mr. Lawson's admirable work on Patent practice is an excellent illustration of the first; and the now old but well-known work of Mr. Hindmarch on Letters Patent is a felicitous adoption of the second. But we do not think a cross between the two can ever be satisfactory. Considering how fully Mr. Lawson's work meets the needs of practice, and how much more convenient it is in point of size than the book now before us, we think Mr. Edmunds would have done better to have

devoted himself to the production of a treatise on substantive law only. A new work on Patent practice was not required by the legal profession, but a new work on substantive Patent law has long been a public desideratum; and we think the present author, with his industry and evident ability, might well have supplied that want. We are afraid, however, that that want still remains to be supplied.

Coming to what is the text of the book-Part I., Patent Law and Practice--we notice that Mr. Edmunds gives in his first three chapters an interesting historical account of the origin of English Patent law. But we are dis

appointed to find that the very important question of subject-matter is but scantily treated in a chapter of thirty-four pages. This in a work of nearly 1000 pages, claiming to be an exhaustive treatise, is a surprising deficiency. In this part of his book, Mr. Edmunds has, in fact, limited his space far too much, and betrayed a tendency to huddle important cases into footnotes-a tendency the more to be regretted considering the size to which the book has otherwise been allowed to grow. In his chapters on specifications and infringement, the author has been much more successful, and these show great care and considerable merit. The chapters on foreign and colonial Patent laws are interesting, but necessarily short,

and where a statement of law has to be so condensed its utility must be very doubtful. The table of cases is very complete, and it is a useful addition to the usual citations to add, as Mr. Edmunds has done, the dates of the decisions. The appendix of forms is a very full one, and the index seems to be well compiled. The immense increase in the number of patents granted by the Crown in recent years has given to this department of our law a greatly enhanced importance, and while we have not scrupled to point out what we regard as the defects of Mr. Edmunds's work, we doubt not that the book will have a large circulation amongst those whose professional duties lead them to consult works on this branch of English law.

OUR BOOK SHELF.

D.Ph. Lessons on Health. By Arthur Newsholme, M.D., (Univ. Lond.). (London: W. H. Allen and Co., 1890.) Up to the year 1889, the Science and Art Department of South Kensington required that candidates for the expassed the Departmental test in physiology. Since that amination in hygiene should at some previous time have date, however, the Science and Art authorities have decided that the hygiene paper shall contain questions on physiology, embracing the general structure of the human body, the forms, positions, and uses of the more important organs, more especially the construction and action of the circulatory and respiratory systems, and of the digestive and excretory organs; and that a separate examination in this subject shall be dispensed with. Dr. Newsholme's "Lessons on Health" is a manual designed to cover the requirements of the elementary stage of the hygiene examination under the altered regulations. Writing for elementary readers, the author wisely begins by devoting a chapter to the chemistry of the chief elements which enter into the composition of the body. The next four chapters are taken up with histology and physiology, but here we do not think the author has entered sufficiently into detail to enable beginners to grasp the full meaning of what they are reading. Our objections have special reference to the histology. For example, the author tells us that the tissues, when examined microscopically, are found to consist of cells, which, in the case of muscular and connective tissues, have become transformed into fibres; and that the original appearance of cells is best seen in the cells of connective tissue, brain, and epithelium. No explanation, however, is given as to what is meant by a cell; nor even a brief account of the appearances and structure of the other tissues of the body; so that, when the reader comes to learn such facts as that the stomach is composed of four different coats, or that there are three layers in the wall of an artery, the latter differing from a vein in possessing more elastic tissue, he cannot form any

adequate idea as to the meaning of these words. Again, in the description of the skeleton, the sterno-clavicular articulation is mentioned, but no allusion is made to the joint between the clavicle and scapula; the ulna is said to articulate with the humerus, but no mention is made of the fact that the head of the radius enjoys the same privilege.

The matter in the hygiene section of the book, both in arrangement and description, is excellent, and may be cordially recommended for the purpose intended. J. H. E. BROCK. Practical Inorganic Chemistry. By E. J. Cox, F.C.S. (London: Percival and Co., 1890.)

THIS is a volume of 51 pages, consisting of "the neces sary notes, reactions, and analytical tables constantly

required for reference" by students preparing for the elementary stage examination of the Department of Science and Art in practical inorganic chemistry. As only seven bases and four acids are included in the syllabus, and the mixtures given are soluble in water or dilute acids, the scope of the volume is very limited. The author begins by stating the possible number and character of the constituents of mixtures that come within the range of the syllabus, and then gives a list of all the substances available for the examiners to make the mixtures from. Then follow lists of reactions and tables of methods. After these is a quotation from the published description of that part of the examination that consists of questions to be answered, and as the examiners state that "the value of the answers will be greatly enhanced by neatness and clearness of sketches," the author proceeds to give "the sketches required," a series of 21 figures all duly labelled, and which presumably includes every sketch that can possibly be needed. The student is recommended to practice copying the figures until he "can draw the apparatus neatly and accurately."

Notes on Trigonometry and Logarithms. By Rev. J. M. Eustace, M.A. (London: Longmans, Green, and Co., 1890.)

THIS work is not like an an ordinary text-book, but consists of a series of well-arranged notes on the elements of trigonometry and logarithms. The subject is treated so that it may be useful to beginners, and to those working it up by themselves. The book-work will be found fully worked out, and, in each chapter, examples on it are given to demonstrate the methods of solution.

Great care has been bestowed on the explanations of the various manipulations to which logarithms can be applied, and the author has reprinted some pages of the mathematical tables published by Messrs. W. and R. Chambers, giving a full explanatory account of the method of using them, which to a beginner will prove most serviceable. Two excellent chapters on solutions of triangles and heights and distances give the student a good insight into the more common problems that are generally worked out in this way.

Miscellaneous propositions and examples are dealt with in the last two chapters: in the former, such propositions as the nine-point circle, distance between centres of circumscribed and escribed circles of triangles, &c., are discussed; while in the latter we have a series of well-selected examples taken from the usual sources. Elementary Statics. By the Rev. J. B. Lock, M.A. (London: Macmillan and Co., 1890.)

The

MANY are the treatises which deal with the subject of elementary statics, but few can rival in clearness the present stereotyped edition of Mr. Lock's work. alterations that have been made have not necessitated any considerable change in the character of the book. By the addition of some fully worked out illustrated problems, and of a carefully graduated set of interesting examples for the student to solve, the author has slightly enlarged the scope of the treatise. The number of the miscellaneous examples at the end have been greatly increased by the insertion of problems that have appeared in the Cambridge examinations in the last two or three years. The subject throughout is treated in the author's best style, and the book can be cordially recommended for the use of beginners.

Die photographische Retouche in ihrem ganzen Umfange. By Wilh. Kopske. (Berlin: Robert Oppenheim. 1890.)

In order to remove the defects incidental to photographic pictures, a process of "touching up" has to be resorted to, and the present pamphlet of 80 pages in length offers instructions in this subject, which will be found of use

by practical photographers. The amount of valuable information compressed within the compass of the little work before us is quite remarkable, and shows that the author is thoroughly familiar with this branch of his art. We can commend the book to photographic artists.

LETTERS TO THE EDITOR.

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

Photographs of Meteorological Phenomena.

AT the Leeds meeting of the British Association a Committee, consisting of Mr. G. J. Symons, F. R.S. (Chairman), Prof. Raphael Meldola, F.R.S., Mr. John Hopkinson, and myself, was appointed to report upon the application of photography to the elucidation of meteorological phenomena, and to collect and register photographs of such phenomena.

The success with which these instructions can be carried out

necessarily depends in a great measure upon the voluntary

co-operation of others.

Will you therefore allow us to appeal to photographers through the medium of your columns, and to ask all those who have in their possession negatives of clouds, lightning, hoar-frost, hailstones, or any other meteorological phenomena, or of damage done by whirlwinds, tornadoes, or storms, to communicate with me?

We shall be grateful for copies of any such photographs, but shall especially welcome offers of future assistance in the shape of photographs taken in accordance with some simple instructions which will be supplied on application.

ARTHUR W. CLAYDEN. Warleigh, Tulse Hill Park, London, S. W., November 18.

Some Habits of the Spider.

THE experiment given by Mr. Boys can be successfully made with a common table-fork. The spider will seize the handle and grapple with it in a ridiculous fashion, but it soon tires of the performance. The prongs will continue vibrating for some little time if struck smartly on a wall.

A curious habit of the spider has perhaps been recorded, but I have never seen it noted. A large, dark spider is sometimes seen in the centre of a strong and regular web. Blow the spider with a slight puff, and if it does not fall or run away, it will shake itself violently for a quarter of a minute. These oscillations are not natural, as the spider will only produce them once or twice, and the natural oscillations are slower. The motion is circular and very rapid, so that the outline of the spider disappears and a blurred appearance three or four times as large as the spider is produced.

This habit is probably protective. Birds would be puzzled rather than frightened, and would find it difficult to make a good shot at the spider. The species of spider is fairly common in gardens and hedges, and is abundant in parts of Norway. It is A. S. E. dark, with a few light spots.

Newton's Rings.

WHILE arranging some experiments on the interference of light for class illustration at the Working Men's College, Melbourne, with a friend, Mr. Wilfred Kernot, of this city, we came across a method of showing Newton's Rings which I have not seen described, and which may be new to some of your readers, though probably any who have had to arrange the experiments for themselves will have come across it.

The apparatus used was a pair of glass plates, 2 inches square by inch thick, squeezed by a pair of clamps at the centres of a pair of opposite edges. A beam from an electric lamp (900 candle-power) was sent through the plates so as to be partly reflected and partly transmitted, and the images formed by these two beams were received on a pair of screens about 5 feet from the plates. Holding the plates at an angle of about Io with the incident beam, the complementary colours are shown with great brilliancy on the screens; by varying the in

clination of the plates to the beam the colours can be changed at pleasure.

In this form the experiment is well suited for class illustration; care is necessary to avoid irregular reflection at the edges of the plates; we covered ours with ordinary gum paper.

B. A. SMITH.

Working Men's College, Melbourne, October 10.

Mutual Aid among Animals.

RECENT discussion of this subject has recalled my attention to an observation made some time ago, while studying the animals of Casco Bay, on the coast of Maine.

Among the specimens brought back from one excursion were four of the common Echini (E. drobachiensis). The last one taken had been left exposed to the sun some time before it was noticed and properly cared for.

These four animals were placed alone in a small aquarium, and, as we wished to study the action of the ambulacra, each was turned mouth up. Soon the action began, with which every naturalist is familiar, and three of the captives slowly rose on edge, and then deliberately lowered themselves into the normal position. The fourth, the injured one, made much less rapid progress all it could achieve was a slight tipping of its disk. The two nearest Echini, from six to eight inches distant, now moved up and stationed themselves on opposite sides of their disabled comrade.

Fastening their tentacles for a pull, they steadily raised the helpless urchin in the direction in which it had started. As soon as it was possible, one of the helpers moved underneath the edge of the disk on the aboral side, and, when the half-turn was accomplished, the other took station on the oral side, gradually moving back as the object of so much solicitude was very gently lowered to the position nature had made most convenient. This is the best instance of " giving a lift I have ever met with among animals of so low a grade. It may not be without interest to others. WM. ELDER.

Colby University, Waterville, Maine, U.S.A.

The Chrysanthemum.

THIS being the centenary year of the introduction of the Chrysanthemum into England, a word on the subject from its native place, Peking, may not be out of place. It is not generally known that the Chinese grow the Chrysanthemum as a standard tree especially for selling. They graft them on to a stalk of Artemisia. There is a species of Artemisia that grows wild and covers the waste ground round Pekin; it springs from seed every year, and by the autumn attains to a tree 8 or 10 feet high with a stem 1 inch thick. The Chinese cut it down, and, after drying it, use it as fuel; the small twigs and seeds are twisted into a rope, which is lighted and hung up in a room to smoulder for hours; the pungent smell of the smoke drives out the mosquitoes. This plant, after being potted, is cut down to about 3 feet and used as the stock, the twigs of Chrysanthemum are grafted round the top, and it quickly makes a fine tree, the flowers grow and open, and as the stock soon withers the whole tree dies, and folks say, "another ingenious fraud of the Chinamen."

If

A favourite style of growing Chrysanthemums is in the shape of a fan, with eight or ten flowers in different parts of it. the flowers are not grown on the plant, they are tied on, which also does for selling.

The winters in Peking are very cold, and last about four months, and having no glass houses the Chinese gardeners do not have the chance of producing such a variety or such fine flowers as their European brethren, but in the case of Chrysanthemums they have many curious and beautiful varieties. THOS. CHILD.

Dispersal of Freshwater Shells.

I AM putting together such instances as I can find of dispersal of freshwater bivalves by closure of their shells so as to cling to the toes of birds, amphibia, water-beetles, &c., and of univalves by adhesion to the wing-cases of water-beetles, &c., and venture to ask for co-operation. Any notes or references which your readers may have the kindness to send to the undermentioned address will be welcomed and carefully acknowledged. H. WALLIS KEW.

5 Giesbach Road, Upper Holloway, N.

The Common Sole.

THE post-larval flat-fish obtained in 80 fathoms off the west of Ireland, which in NATURE (vol. xlii. p. 520) I referred to as common sole, have turned out, on closer examination to be the fry of Pleuronectes cynoglossus, called "white sole" in the Dublin markets.

I shall feel obliged by your finding space for this correction.
Dublin, November 15.
W. SPOTSWOOD GREEN.

The Scientific Investigations of the Fishery Board for Scotland.

IN the review of the "Eighth Report of the Fishery Board for Scotland," which appeared in NATURE (vol. xlii. p. 653), the reviewer, misled by the private information to which he refers, makes an inaccurate and baseless statement, reflecting upon me personally, and which I therefore crave leave at once to correct. In dealing with my report on immature fish, which, by the courtesy of the Secretary for Scotland, was placed in the hands of the delegates of the recent International Fisheries Conference, and which has already been referred to in your columns by Prof. McIntosh, F.R. S., the reviewer states: "We have certain information that the original discoveries which led to this report were made" by Mr. T. Scott; and that "it is only fair that the credit which is Mr. T. Scott's due, and which is denied him there, should be acknowledged here."

Had your reviewer disregarded his private information, and looked at p. 161 of the paper which he has reviewed, he would have found there the following footnote to the statement that "nearly 13,000 food-fishes" had been "carefully measured, and the condition of the reproductive organ registered," viz., "This has been mainly done by Mr. Thomas Scott, F.L.S., one of the naturalists of the Fishery Board, and partly by Mr. Peter Jamieson, assistant naturalist."

What Mr. Scott and Mr. Jamieson did was precisely what is stated-namely, to measure the length of the fish and record on the form provided whether the milt or roe was mature or not. The subjoined note from Mr. Thomas Scott, which I request you to publish along with this, shows that he considers this acknowledgment sufficient. The study and elaboration of these daily records, nearly 13,000 in number, mainly in my private time, was only a part, and a small part, of many months of labour bestowed on my report on immature fish; and the results Occupy less than three pages of the fifty-four devoted to the subject. No other person had any part or share whatever in the conception or composition of that report, and this attempt to deprive me of the credit of my work, solely on the strength of private and erroneous information, is not, I think, either usual or creditable.

The reviewer is equally in error as to what I wrote in the Report for 1887, and which he only partially quotes. The entire sentence is as follows: "We have organized a series of extensive and systematic inquiries into the condition of the reproductive organs of the various kinds of fish throughout the year, with particulars as to their sizes, the nature of their food, &c., which will help to clear up the hitherto obscure problems as to the minimum size of sexually mature individuals, the commencement and duration of the reproductive period, the spawning will now peruse p. 8 of the Seventh Report, he will find it places, and many other points of great interest." If the reviewer there stated that these inquiries were "devised by Dr. Wemyss Fulton" (in 1887), which is the fact.

T. WEMYSS FULTON. 20 Royal Crescent, Edinburgh, November 3.

14 Lorne Street, Leith, November 1. DEAR SIR, I have read the article in NATURE of October 30, and desire to say that I consider the footnote at p. 161 of part iii. of the Board's Report for 1889 a sufficient acknowledgment of my work in connection with the immature fish investigation. You have always from the first acted towards me in a very friendly manner, and would be the last to detract from any credit belonging to me.

THOMAS SCOTT. Dr. T. Wemyss Fulton, Secretary Scientific Investigations.

Araucaria Cones.

HAVING been away from home, I have only now seen the Duke of Argyll's letter in NATURE of November 6 (p. 8), relating to the cones of Araucaria. Doubtless before this some of your correspondents have answered the Duke's inquiry.

It is not very unusual for the Araucaria imbricata to produce cones. The first I myself remember to have seen were on the old tree in the Royal Gardens, Kew, in the summer of 1851 or thereabouts. The female cones are large globular masses, the constituent scales of which are not (superficially) very different from the ordinary leaves. What the Duke describes are evidently the male catkins. The trees are ordinarily dioecious, but I have once seen and figured an example in which male catkins and female cones were borne on the same tree. London, November 14.

MAXWELL T. MASTERS.

IN the garden of the house Bleckley, Shirley Warren, Southampton, there is an Araucaria that for many years past has produced annually a large number of cones. The cones are from 40 to 100 in number, and very large, so that their breaking up and falling on to the lawn is a serious inconvenience, it being difficult to sweep them up. No fertile seeds have been produced by this tree, which from all I have been able to learn is the finest Araucaria in England; the trunk is over 6 feet in circumference some 2 feet above the ground. There is no history of the tree. Cambridge, November 15. D. SHARP.

IF the Duke of Argyll refers (November 6, p. 8) to ovulebearing cones, which are spherical and about 7 inches in diameter, these have been plentifully produced in almost every part

of the British Isles.

Male or pollen cones (catkins), of cylindrical shape and 3 inches long, are, however, extremely rare, although they have been produced in the Bicton Pinetum and on one of Earl Derby's Kentish properties. A tree at the latter place bears annually, and has done so for some years, a heavy crop of perfectlydeveloped pollen cones; indeed, so great is the quantity that at a short distance away the tree has quite an unusual and remarkable appearance. A. D. WEBSTER.

Holwood Estate, Kent, November 17.

ATTRACTIVE CHARACTERS IN FUNGI.

THIS HIS subject, which has been introduced by a letter from a correspondent (November 6, p. 9), is one of considerable interest, but it is one also of great mystery and difficulty. In dealing with fungi of the mushroom type we are in contact with a class of plants so different from Phanerogams that it is at once evident that we must not draw the same conclusions from a similar series of initial facts. It is well known that certain fungi possess strong and characteristic odours, and others very conspicuous colours, both of which features are presumed to have some value in the biography of the plant, but what influence and what value it is not so easy to determine as in the case of plants in which cross-fertilization has to be effected. It is by no means certain that there is any special act of fertilization at all; it is even doubtful if any fertilizing element exists. For nearly a century it has been thought possible to find a fecundating element in Agarics, but all efforts at demonstration have failed.1 Most of these investigations have been directed to the cystidia, large cells which are recognized as projecting, more or less, on the surface of the hymenium, but these could not be identified with any known process of fecundation. M. de Seynes, after patiently investigating the hymenium of the Hymenomycetes, arrived at a negative result, and this has not since been disturbed. "The hymenium," he says, "has not yet offered an organ which we may suppose in reality to be the male organ ;" and he adds, one sole and self-same organ is the basis of it, according as it experiences an arrest of its development; as it grows and fructifies, or as it becomes hypertrophied, it gives us a paraphysis, a basidium, or a cystidium; in other terms, atrophied basidium, normal basidium, hypertrophied basidium: these are the three elements which form the hymenium. Does it develop either outside the hymenium or on the hymenium, at a time, or in a part which has not yet been discovered, organs which yield De Bary, "Morphologie und Physiologie der Pilze," cap. v. * See Grevillea, vol. i. (1873), p. 181.

pollen, spermatia, antherozoids, or any other fecundating agent? This is what remains to be discovered." 1 Amongst British mycologists Mr. Worthington Smith has been the most persistent in belief that Agarics are subject to hybridism, which implies cross-fertilization, but

he has not contributed much towards the establishment of the proposition that fertilization really exists, except perhaps to emphasize the suggestion that the cystidia are male organs. In his paper on the reproduction in Coprinus radiatus, he remarks: "I consider it quite possible that the mere contact of the threads (or fluid) from the cystidia with the threads from the unpierced spores may be sufficient for the production of a new plant." In more direct reference to the question of hybridism he writes :"On a dung-heap, which will produce Coprinus radiatus, other species, as C. nycthemerus, &c., are sure to appear; and not only do allied species come up in company with C. radiatus, but every intermediate form between one and the other may be gathered any morning. These latter plants belong to no species described as such, but are natural hybrids, doubtlessly produced by the spermatozoids of one plant piercing the spores of another. Amongst the larger species of Agarics similar forms are quite common, and they prove sore puzzles for those men who only want names for the fungi they find."

No one with any extended experience in field work can gainsay that individual Agarics are often met with which strongly suggest hybridism. These forms are so intermediate between more typical forms, with which they were perhaps growing, that it is difficult to get rid of the idea altogether that they are modifications due to some such influences as in higher plants we attribute to hybridization. It would be very unphilosophical to deny absolutely that they are possibly hybrids; but, on the other hand, it would be as bad to declare them hybrids until some sort of impregnation can be demonstrated.

Admitting that hitherto all efforts to discover any process of fertilization in Agarics, which will stand the test of examination, has failed, the difficulty is increased in speculating upon the "why and wherefore" of the phenomena of odour, taste, and colour, in the larger fungi. Yet, notwithstanding this, we may approach nearer the desired end by endeavouring to collect facts, which may some day, by accumulation, serve as a basis for hypothesis.

Why do certain fungi possess very strong odours, which to our olfactory nerves are agreeable or disagreeable? There is a small whitish Agaric, not uncommon amongst grass in woods, which has such a strong and peculiar odour that it is named Agaricus (Clitocybe) fragrans. It is not more than about an inch in diameter, is mild to the taste, very pleasant to eat when cooked, and the odour remains after the plant has been dried for some time. Some persons detect in it a resemblance to anise, others to melilot, or the Tonquin bean, and others again regard it as an odour peculiarly its own. Two or three other species, to be found in similar localities, might, at a glance, be confounded with it, but that they are destitute of the odour and pleasant flavour. The novice could at once distinguish this fungus from its associates by its odour, but wherefore it should smell so sweet whilst the others do not is at present an unsolved mystery. It is certainly not specially attractive to insects, and we have never found it attacked by slugs; perhaps the odour is disagreeable to them.

Another Agaric may be found amongst dead leaves, which is twice as large, and of a singular pale verdigris. green colour (Agaricus (Clitocybe) odorus). It possesses very nearly the same odour, possibly a little stronger, and the same agreeable taste. This, again, we have always observed to be free from any indication of attacks from slugs. We have failed to detect the same odour, except

Grevillea, vol. ii. p. 41.

2 Grevillea, vol. iv. (1875), P 53.