68 Morphology BOOK i 



of metamorphosis into harmony with the whole of the 

 vegetable kingdom. The alternative, to admit that the 

 conception of leaf and stem as different, but equally 

 essential, members, only became evident after a certain 

 course of evolution, and that consequently the metamor- 

 phosis of a member could only be conceived of as taking 

 place in a certain section of the vegetable kingdom, destroys 

 its fundamental character, and therefore reduces, or even 

 minimizes the importance of the theory. 



The idea that the so-called trichomes are morphologically 

 co-ordinate with the phyllome and the caulome is also 

 open to serious criticism. Trichomes arise indifferently 

 and irregularly from both the others, and their identification 

 depends upon anatomical and not morphological features. 



The position of the sporangium in the scheme of 

 members was again a difficulty. Its true homologies were 

 only gradually brought to light : in some cases it appears 

 to be an epidermal outgrowth, and hence a trichome. 

 In others, arising on a leaf, it seems to be a part of the 

 latter ; springing from a stem the theory of metamor- 

 phosis pronounces it to be a phyllome. It was not till 

 1881 that it was recognized as an independent member, 

 corresponding to none of the others, but being sui generis. 

 Its identification as such was made by Goebel in a paper 

 published in the Botanische Zeitung in 1881, and it met imme- 

 diately with general acceptance. The recognition need not, 

 however, be taken as necessarily antagonistic to the theory 

 of metamorphosis, as it may be said only to add another 

 member to Wolff's list. On the other hand it can hardly 

 be fundamental, as its occurrence is restricted. 



Bower carried this idea still further, when he suggested 

 in 1894 that the sporangiophore also should be regarded 

 as a member sui generis. 



The study of the Cryptogams was soon found to involve 

 the recognition of adaptation to environment to a greater 



