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OF BOTANICAL DRAWINGS.
Another important method of indicating and preserving the characters of plants is by means of botanical drawings; which, if carefully executed, and accompanied by magnified analyses of the parts that are not visible upon external inspection, are the very best means of expressing the peculiarities of a species. But, to render drawings really useful, there are many circumstances to be attended to.
In the first botanical works that were illustrated by figures, the drawings were rude, and ill calculated to convey any clear idea of the object they were intended to represent: but, as a knowledge of the science advanced, great improvement took place in their execution ; minute accuracy was introduced into the outline of the leaves; the form and position of the flowers were carefully expressed ; and, if the parts of fructification were neglected, it was because their importance was not understood. By degrees, the analysis of those parts began to be attended to; attempts were made, with various success, to represent the minute points in the organs of fructification, At last, the subject of carpology was taken up by the celebrated Gærtner, who published two quarto volumes, in which numerous plates represented, often in a magnified state, the internal structure of fruits, and especially of their seeds. From the appearance of this work, I think, it is, that decided improvements in the drawings of the analysis of flowers may be dated. Since that period botanical drawings have been gradually improving, till, at last, many have been executed which seem to leave nothing to be desired.
A botanical drawing should represent a branch of the plant in flower, and also in fruit, of the natural size, in which all the characters of the leaves and ramifications, the direction and relative position of parts, the mode of expansion, the arrangement of the flowers, and, in short, all that can be seen by the naked eye should be accurately expressed. It should also contain analyses of all the parts of fructification, magnified so much that every character may be distinctly seen; and this analysis, to be complete, should express the state of the organs of fructification, not only at the period of the expansion of the flowers, but in the bud state, and when arrived at perfect maturity. If to this the germination and vernation, and highly magnified anatomical representations of the tissue and internal structure of the stem and leaves, be added, the drawing may be considered complete.
But as the expense of preparing and publishing such drawings would be enormous, botanists usually content themselves with a representation of those parts only that are supposed to be most essential; such as the structure of the flower when expanded, and of the fruit and seed when ripe; and this is found, for systematic purposes, sufficiently complete, provided such details as are introduced are perfectly clear and correct.
In order to enable the student, who is interested in this subject, to form a more distinct notion of the relative utility of botanical drawings, a reference to some of the most perfect that have yet been executed is subjoined.
As instances of the highest perfection of which botanical drawings are at present susceptible, the volume of illustrations of the structure of Wheat, by Francis Bauer, preserved in the British Museum; the analysis of Rafflesia, published in the 12th volume of the Linnean Transactions ; the drawings of New Holland plants in the Appendix to Flinders's voyage to that country, and the three fascicles of figures of New Holland plants by Ferdinand Bauer; with the microscopic drawings of the fructification of Orchidaceous plants, now in course of publication, by the former distinguished artist, may be justly said to be entitled to the first place. A high station is also claimed by Hooker's figures of British Jungermanniæ, in which great artistical skill is combined with accurate, and for the time extensive, microscopical research.
Among works in which fewer details are introduced, espe
cial mention must be made of the drawings of Palms, and the figures that illustrate Von Martius's Nova Genera et Species Plantarum ; Turpin's plates in Humboldt and Kunth's Nova Genera Plantarum, and in Delessert's Icones Plantarum ; and some excellent analyses of the parts of fructification of Rhamnaceæ and Bruniaceæ, in his memoirs upon those orders, by Adolphe Brongniart.
Almost every scientific work of reputation, of the present day, contains figures which are formed upon the models of those now enumerated; from which they differ in the quantity of analysis that is introduced, a circumstance generally regulated by the price at which they are published.
Of anatomical plates, the best are those of Link, in his folio work on vegetable anatomy; of Mirbel, in his Mémoire sur l’Ovule ; of Adolphe Brongniart, in his various papers in the volumes of the Annales des Sciences; and especially of Mohl, in his illustrations of the anatomy of Palms and Tree Ferns.
I have mentioned these as instances of good drawings, because they are easily accessible, and incontestably are ell adapted to improving the taste and execution of a student; but there are other modern works, in which the figures may be also studied with great advantage. Whatever bears the name of Francis or Ferdinand Bauer, Hooker, Greville, Mirbel, Decaisne, Schleiden, L. C. Richard, Miss Drake, Mohl, or Turpin, may almost always be profitably studied.
A very ingenious method of obtaining photogenic drawings, or fac-simile representations of plants, by the action of light upon paper prepared with some of the salts of silver, has lately been invented by Mr. Henry Fox Talbot ; and the art, if it should prove possible to use it for practical purposes, would be of great value: but too little is as yet known of its application, to enable me to speak confidently upon this point.
Page 10. The only case of undoubtedly perforated parenchyma with which I am acquainted is in Sphagnum, where it was first noticed by Mr. Valentine (Muscologia Nottinghamiensis, No. 1. 1833). He correctly describes this genus as having the exterior cells of its branches furnished with an aperture communicating with the external air. “ The aperture is tolerably distinct in S. acutifolium ; it is situated at the upper end of the cell, and stands off obliquely, appearing like a minute truncated cone. An easy way to observe it is, to press out the air contained in the cells, which escapes from the aperture in a minute bubble.” This curious contrivance might have been supposed analogous to the air passages into the trunk, below the insertion of the leaves of Tree Ferns, if it did not equally exist in all the parenchyma of the leaves themselves. Mr. Valentine does not notice the latter fact, and I believe he considers the circles in the leaves of Sphagnum not to be apertures: but I had ascertained, by Mr. Reade's ingenious charring process, that they undoubtedly are openings, before I saw John Röper's paper upon the subject in the Annales des Sciences (n. s. X. 314.). This writer determined that the circular spaces in Sphagnum leaves are openings, by observing the exit and entrance. through them of the Rotifer vulgaris, and of minute granular matter. He considers the openings intended “ to guarantee the organs
of respiration from the too great influence of the air.” But I do not perceive in what way such an effect is to be accomplished.
Page 32 Spiral vessels certainly exist in the roots of many exogens; in the Parsnep and the Beet they are large, and readily extracted entire.
With regard to their existence in seeds, Mr. Quekett has favoured me with the following memorandum (March 13. 1839) :If you place almonds in boiling water, and separate the testa, and while thus softened you scrape or remove some of the veins which figure its surface, it will be found that they are almost wholly spiral vessels, which are of rather minute dimensions.
“ There is something else curious respecting this seed. On its surface are numerous projecting cells which have very thick parietes : these can be found burst and their contents emitted ; in fact they look more like eggs of some minute insect, which however they are not, as I have examined seeds of unopened almonds, where they exist likewise: they appear to me to be analogous to the cells which exist on the seeds of Cobæa scandens, which Don describes as mealiness, but which is, instead, a beautiful example of fibro-cellular tissue.”
To this I may add, that in the seed of Soymida febrifuga there lies in the middle of the wing a thick stratum of fibro-cellular bodies, which would be regarded as spiral vessels if they were longer and more cylindrical ; but which seem to be a curious and distinct form of fibro-cellular tissue.
Page 43. In addition to the remarks here made upon Raphides, I have the satisfaction to insert in this place the following interesting communication from Mr. Quekett, upon the same subject :
“ General Appearance. — Raphides are most frequently observed under two forms, appearing in one instance as transparent acicular crystals, which are either distinct from each other or united into a compact fibrous bundle, and in the other instance as small bodies composed of many crystals which radiate from the same centre, thereby forming a more or less spherical mass.
- Besides these two usual kinds, there are other forms, but of more rare occurrence, some of which are observed of regular crystalline figure; as the rhombohedron in some cells of Calla æthiopica, and bark of Cascarilla ; octohedron, according to Meyen, in the stem of Tradescantia virginica; the rectangular prism in Quillaja saponaria ; and oblique prisms, which occur with acicular crystals, in Scilla maritima: but still there are a few varieties which present an irregular crystalline figure, some of which can be observed also in Tradescantia virginica, and in the inner layers of the bark of the Lime tree, where they seem very thin and pointed at the extremities, appearing like slices cut longitudinally from the middle of a square prism, which may be imagined to possess a foursided pyramid at each end.
“ Form. — With respect to the form of the acicular Raphides,