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 illustrated in Figure 28 a. If preferred, such thick-walled elements may be entirely represented by thick black lines as in Figure 28b, and when such cells are relatively few in number, this method has much to recommend it since a greater relief is obtained.
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| Fig. 28.A transverse section to shew |
Finally, an attempt may be made to draw in a more detailed fashion as in Figure 28c. Here the thickness of the cells of the wood is represented by broad black lines, the middle lamellæ 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 illustrated in Figs. 29 and 30.
