IN THE VEGETABLE KINGDOM. 53 



Sanderson* would argue from this a homology between 

 the structures standing in the most direct relation to these 

 processes that is, between the foliaceous axis of the moss 

 and the prothallium of the fern, as the parts which bear 

 the sexual elements ; and again, between the leaf-bearing 

 stem of the fern and the theca of the moss, as immediately 

 derived from the impregnated germ, and as originating the 

 succeeding phase by a gemmiparous process (the formation 

 of spores). Without at present entering into any argu- 

 ments of a general nature on the correctness of this view, 

 it may be simply remarked that the primd facie aspect 

 suggests rather a homology between the leaf-bearing stems 

 in the two orders, in which case we should ascribe the 

 different relations between them and the reproductive 

 organs to the interposition of a process of gemmation at 

 different periods of the genetic cycle that is, just before 

 impregnation in the fern, and immediately after it in the 

 moss. Not that the resemblance is merely of a primd facie 

 kind. In some respects it grows upon us the more we con- 

 template it, for the persistent character of the leafy axis of 

 the moss, and its frequently yielding many successive sets 

 of sporiferous capsules, assimilate it, independently of struc- 

 tural features, rather to the stem of the fern than to its 

 prothallium, which is an organ even more evanescent than 

 the capsule of the moss, its existence terminating when the 

 embryo formed in it has begun to germinate. [ In this 

 view the gamomorphic stage, which is not represented in 

 mosses farther than by the formation of antheridia and 

 archegonia as mere appendages of the typical axis, embraces 

 in ferns and Equiseta the development and dispersion of 

 spores, and their germination into prothallia bearing the 

 sexual organs, either in different phytoids, as is generally 



* Veget. Ovum, in Cyc. Anat. and Phys., Vol. IY. 

 f Jenner in Edin.'Philos. Journal, N.S. III. 269. Eadlkofer, Annals 

 Nat. Hist. 2d Ser. XX. pp. 241, 344, 439. 



