THE USES 



LEAVES IN PLANTS. 403 



longest internodes; and, on the other hand, the more complicated cycles are 

 found only in cases of very short internodes, or in great condensations of leaves. 

 There is no evidence, however, that in the condensed form in which undeveloped 

 leaves exist in the bud the cycles are any more complicated than on the stem. 

 Nor ought we to expect such evidence; for it is a false analogy that would lead 

 us to seek for types in the early and rude forms of embryonic life; though, if 

 the simpler cycles were really derived from the more complicated ones, rather 

 than from the utility common to all, we ought, by the analogy of embryology, 

 to find some traces of the process in the bud. No doubt the types exhibited 

 by the mature forms of life exist in the embryo or bud, though not in a 

 visibly embodied form ; but rather in a predetermined mode of action in vital 

 forces, embodied in gemmu,les rather than the visible germ. But while the dis- 

 tribution effected by the internodes of the stem thus allows the simpler cj'cles 

 to occur, it does not account for their occurrence. This, moreover, must depend on 

 relations in mature, or else in growing leaves, to those below them ; and not on 

 their earlier relations in the bud; since, as we have seen, the more complicated 

 cycles are the best fitted for these relations, and in mature stems are on 

 found in great condensations of leaves ; such as the bud also presents ; yet 

 without any greater complication than the stem has. The simplicity of the 

 cycles in stems with long internodes has the effect that the absolute distance 

 between two leaves standing one over the other is not so great as it other- 

 wise would be. There is, no doubt, a disadvantage in long internodes, or in the 

 separation of growing parts by long intervals from their sources of nutrition; 

 a disadvantage, which only a better exposure to light and air for their subse- 



quent functions could compensate. On the theory of adaptation there would 

 seem to be, then, some advantage to the younger leaf in standing directly over 

 an older one, and not far above it; a greater advantage than in any other 

 position at the same height; and this advantage could apparently be no other 

 than an internal nutritive one, having reference to the sources or movements 

 of sap and the nutrition conveyed by it. But sap circulates with nearly equal 

 facility around and along the stem ; and if the lower leaf were really a special 

 source of nutrition to the growing one above .it, it could furnish nutrition 

 almost as readily to any other position on the stem at the same height as to 

 the point directly above it, or on the same side. The new leaf is not sensibly 

 nearer the market on account of this feature in the arrangement. But may 

 there not be some advantage to the older leaf in standing directly under the 



