BOTANICAL SUBJECTS. 107 



One cannot examine any embryo of a plant without being 

 convinced that its parts are only a continuation or repetition, with 

 modification, of parts belonging to very distant ancestors. In text 

 books the embryo is divided into radicle, caulicle, cotyledons, and 

 plumule. But by reference to the bud of Asplenium decussatum 

 (Fig. 42) it will be seen that these parts are also traceable in the 

 leaf buds of ferns ! 



Neither has the root sprung from the stem, nor the stem from 

 the root, nor the leaf from either, but all from some common 

 basis. That basis may be the homologue of the cellular placenta- 

 like structure which forms the disc of attachment of certain 

 seaweeds, or, if one would care to call it so, ?i primordial node. 



The stem and the root must be considered as two buds of the 

 same cell mass ; that is, a further expansion of it with cell 

 modification. The stem, of course, has developed into a medium 

 different from that, which receives the root, and therefore, and as 

 a matter of course, the nature of each, has in the course of 

 descent been modified, both in form and function to suit 

 surroundings. 



So much are the root, stem, and leaf of one nature that 

 probably there is no part of the living root, stem, or leaf which 

 under certain circumstances might not evolve buds. There 

 may be good reasons why ordinary buds come in places where we 

 find them. It is an inherited habit which was originally forced 

 on the plant by competition.* 



Then, as ordinary buds are produced indifferently on root, 

 stem, or leaf, all three must be different forms of the same thing, 

 however varied their structure may be, and however obscured 

 their nature may be by the nomenclature of authors. Can 

 anything be more leaf-like, or stem-like, than the leaves of 

 Phyllocladus, Xylophylla^ Ruscus, and others ? 



Even if we were not able to see all this with our imagination, 

 the theory of evolution, once accepted, leaves us no choice. 



Asa Grrayl says, " There are, however, reduced forms, in 

 which there is no distinction of axis or foliage, but most of these 

 are clearly leafiess rather than stemless, and not even in Lemna 

 and Woolfia can the stem be said to be wanting (!)." 



If we remain wedded to the distinction between stem and leaf, 

 except in form, we must call Lemna and Wooljia either stem or 



* This point is worked out further under the heading of axillary hid. 

 t Struct. Bot., note to p. 45. 



