. Popular science monthly. s are bulbous. These, moreover, do not be-long to any single group, but are scattered among a large number of very different families : the bulbouscondition can not, therefore, be ex-plained by inheritance, but musthave reference to the surroundingcircumstances. Moreover, in a largenumber of species the leaves tend tobecome succulent and fleshy. Now,in organisms of any given form thesurface increases as the square, themass as the cube, of the , a spherical form, which isso common in small animals andplants, and which in them offers asuflUcient area of
. Popular science monthly. s are bulbous. These, moreover, do not be-long to any single group, but are scattered among a large number of very different families : the bulbouscondition can not, therefore, be ex-plained by inheritance, but musthave reference to the surroundingcircumstances. Moreover, in a largenumber of species the leaves tend tobecome succulent and fleshy. Now,in organisms of any given form thesurface increases as the square, themass as the cube, of the , a spherical form, which isso common in small animals andplants, and which in them offers asuflUcient area of surface in propor-tion to the mass, becomes quite unsuitable in larger creatures, andwe find that both animals and plants have orifices leading fromthe outside to the interior, and thus giving an additional amount ofsurface. But in plants which inhabit very dry countries it is necessarythat they should be able to absorb moisture when opportunity offers,and store it up for future use. Hence, under such circumstances fleshy. Fig. S:9. ON LEAVES. 487 stems and leaves are an advantage, because the surface exposed toevaporation is smaller in proportion than it would be in leaves of theordinary form. This is, I believe, the reason why succulent leavesand stems are an advantage in very dry climates, such as the Canaries,Cape of Good Hope, etc. The genus Lathyrus, the wild pea, contains two abnormal andinteresting species, in which the foliaceous organs give the plant anappearance very unlike its congeners. Fig. 30 represents L. niger,with leaves of the ordinary type. In the yellow pea (X. aphaca, ), the general aspect is very different, but it will be seen on a closer
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1872
