Hatton. (Hatton, _Craftsman's Handbook_.)]

[Ill.u.s.tration: Fig. 19. Hollyhock (_Althaea rosea_). By R. G. Hatton.

(Hatton, _Craftsman's Handbook_.)]

[Ill.u.s.tration: Fig. 20. A Liverwort (_Lepidozia reptans_). (Evans, _Annals of Botany_, 1912, vol. 26.)]

[Ill.u.s.tration: Fig. 21. A Seedling of _Bruguiera gymnorhiza_, a mangrove. Drawn by Mrs. F. E. Fritsch. (Tansley and Fritsch, _New Phytologist_, 1905, vol. 4.)]

[Ill.u.s.tration: Fig. 22

A diagrammatic sketch by Mrs. F. E. Fritsch of _Rhizophora conjugata_, a mangrove. (Tansley and Fritsch, _New Phytologist_, 1905, vol. 4.)]

[Ill.u.s.tration: Fig. 23

A shoot of _Acanthus ilicifolia_, a mangrove. Drawn by Mrs. F. E.

Fritsch. (Tansley and Fritsch, _New Phytologist_, 1905, vol. 4.)]

[Ill.u.s.tration: Fig. 24

A longitudinal section of a fossil seed, _Conostoma oblongum_. Drawn by Dr. E. J. Salisbury. (Oliver and Salisbury, _Annals of Botany_, 1911, vol. 25.)]

[Ill.u.s.tration: Fig. 25

The Meadowsweet (_Spiraea ulmaria_), shewing four years' growth.

(Yapp, _Annals of Botany_, 1912, vol. 26.).]

[Ill.u.s.tration: Fig. 26. The Chesil Bank. (Oliver, _New Phytologist_, 1912, vol. 11.)]

THE DRAWING OF MICROSCOPIC DETAILS.

Questions relating to the drawing of microscope sections may now be dealt with. Usually these are drawn in pencil and reproduced by means of lithography; this is quite wrong, for in addition to its being an unnecessary expense, it is also an inconvenience to a reader, since the figures are necessarily divorced from the letterpress. There are very few histological details which cannot be represented by line blocks, and with a proper co-operation between the author, the block maker, the printer and the publisher, even the delicacies of karyokinesis could be reproduced in the text.

For demonstration purposes, transverse sections of plant-structures may first be taken.

The walls of the various elements may be represented by lines of more or less equal breadth, but in those cases where the walls are particularly thick, _e.g._, the elements of the wood, the thickening may be represented by an additional line. This is seen in Fig. 27, in which it will be noticed that the middle lamellae of the wood-elements are represented by black lines.

[Ill.u.s.tration: Fig. 27.

(From Butler's paper on Gummosis of _Prunus_ and _Citrus_. _Annals of Botany_, 1911, Vol. 25).]

This is a particularly good drawing, but, unfortunately, it has been over reduced.

On the other hand, the various tissues may be represented by lines of varying breadths, the thickest walled cells having the same double contour as in the above, but with the addition of local colour in the shape of diagonal shading. This is not uncommonly found in papers dealing with the anatomy of plants by French authors; it is ill.u.s.trated in Figure 28 _a_. If preferred, such thick-walled elements may be entirely represented by thick black lines as in Figure 28_b_, and when such cells are relatively few in number, this method has much to recommend it since a greater relief is obtained.

[Ill.u.s.tration: Fig. 28

_a_

_b_

_c_

A transverse section to shew the vascular cylinder of the root of the spinach, _c_ is somewhat older than _a_ and _b_.]

Finally, an attempt may be made to draw in a more detailed fashion as in Figure 28_c_. Here the thickness of the cells of the wood is represented by broad black lines, the middle lamellae being left white.

The lines marking the boundaries of the other cells vary slightly in thickness, but this is to a great extent masked by the representation of the cell contents, which consist entirely of dots in the case of the protoplasm, whilst the nuclei are represented by dark ovals--black relieved with small white areas. By varying the size of the dots and their distance apart, varying densities can be indicated.

It has been mentioned above that it is possible to reproduce fine detail by means of the line block; this is ill.u.s.trated in Figs. 29 and 30.

[Ill.u.s.tration: Fig. 29]

Fig. 29, which ill.u.s.trates a stage in the division of a nucleus, was drawn with black crayon on a rough-grained piece of Whatman's water-colour paper. The cytologist will, doubtless, criticize its coa.r.s.eness, but it may be mentioned that the roughest paper at hand was designedly employed in order to ill.u.s.trate the point raised. That a finer grained paper will give more delicate results is shewn by Fig.

30, which is a reproduction of a drawing, kindly lent by Dr. W. G.

Ridewood, made with ordinary lead pencil on grained Bristol board. Its delicacy is obvious, and at first sight it could easily be mistaken for a lithograph.[A]

[Footnote A: Many similar examples will be found in Ridewood's memoir _On the Cranial Osteology of the Clupeoid Fishes_, Proc. Zoo. Soc., Lond., 1904, vol. 11, p. 448.]

[Ill.u.s.tration: Fig. 30]

A half-tone can be put on to a line block during its manufacture. All that the draughtsman has to do, is to indicate by blue pencil lines those parts on which he requires the dots, which give the half-tone, to be placed, and to select the pattern of the stipple he desires to be used. The result may appear somewhat mechanical since the dots are regularly arranged, but a drawing sometimes may be considerably improved by this means if used with judgment. It is frequently employed in representing drapery, and many examples may be found on those pages of newspapers devoted to ladies' dress (Fig. 31; see also Fig. 32).

[Ill.u.s.tration: Fig. 31. After a water-colour design by Miss Winifred Pea.r.s.e.]

THE DRAWING OF DIAGRAMS AND APPARATUS. Much valuable information may be conveyed by diagrams; in fact, these could be used more freely than they are.

[Ill.u.s.tration: Fig. 32]

The principles to be borne in mind are the same as for other ink drawings. They should always be drawn upon an enlarged scale, and with as little detail as possible, which generally should be indicated in the most conventional ways--dots, black s.p.a.ces, lines, and so on (Figures 33 and 34). The main thing to be aimed at is clearness, so that it is often necessary to sacrifice true relative proportions in order to gain this end (Fig. 34).

[Ill.u.s.tration: Fig. 33. A diagram by Mr. E. Lee. (_Annals of Botany_, 1911, vol. 25.)]

[Ill.u.s.tration: Fig. 34

A Diagram from the _Annals of Botany_, 1912, Vol. 26.]

In certain cases it is possible to combine detail and diagram in one drawing; this is shewn in Fig. 32, taken from Dr. Ridewood's admirably ill.u.s.trated memoir on the _Gills of Lamellibranchiata_ (Transactions of the Royal Society of London, B. vol. 195, 1903). The shading employed was either done by the draughtsman (at _ch_ and in the cells with irregularly arranged dots), or else was put on the block during its manufacture (_af_). If a lens be used, the difference will at once be obvious.

The finished drawing should be bold and neat, and all lettering should be very clear. If several figures are included in one diagram they may be separated one from the other by ruled lines, and in no case should one tier of figures--taking the frames as the boundaries--unevenly overlap another tier, otherwise the diagram, to use an expressive phrase, will look "like a pig with one ear."

Under the heading of diagrams must be included the representation of apparatus. There are two ways of drawing apparatus; the objects may be drawn as a study in still life, as, for example, in many of the figures ill.u.s.trating Deschanel's _Natural Philosophy_ (London, 1890) or they may be represented in a purely conventional fashion. The latter is the better way, and it is preferable to draw for the most part in section in order that all connections, inlets, outlets, etc., may be clearly shewn.

A study of a good example is infinitely better than a written description, wherefore Figure 35 has been inserted.

[Ill.u.s.tration: Fig. 35]

It will be observed that all gla.s.s vessels and tubing are represented in section, and in the thermometers, the fine capillary bores are represented by a single line in each case; corks by diagonal shading; wood by lines in imitation of its grain; metal parts by vertical shading or dead black; more or less still liquids by a series of lines broken below and continuous at the surface, and gradually becoming closer and closer together towards the surface. Mercury, on the other hand, may be indicated by dead black relieved by a few white lines to represent its reflecting surface, also its free surface may be drawn convex. Finally thumb screws may be shewn by a combination of black areas and vertical shading.

These conventionalities need not all be followed; for instance, rubber connexions may be indicated by broad black lines and wood by diagonal shading.