Goebel. — On the Simplest Form of Moss . 357 
resemble that of the male plant, but are peculiar in that the 
marginal cells can grow out into protonemal filaments. This 
case is similar to that of certain species of Trichomanes , where 
some branches of the filamentous prothallium develop into 
flattened cellular expansions which reveal their filamentous 
origin in that their marginal cells grow out into filaments, and 
to that of the protonema of Sphagnum. 
That the female plant should attain a higher degree of 
development than the male is naturally correlated with their 
respective functions. The male plant has but a short exist- 
ence ; when it has produced and has set free the spermatozoids, 
it perishes. The female plant has to protect and nourish the 
sporogonium during its development, for which a period of 7-8 
months is necessary; consequently the plant must attain a 
relatively high organization. 
The organization of the sporogonium, likewise, is rudi- 
mentary as compared with that of the true Bryineae ; it 
somewhat recalls that of the sporogonium of Sphagnum and 
of Andreaea , and especially that of Diphyscium the second 
genus of Buxbaumieae. It has no true seta, but merely 
an absorbent organ which penetrates into the rudimentary 
stem of the Moss-plant ; this organ gives off a number of 
rhizoids which absorb nourishment from the stem. Conse- 
quently in this form the calyptra is ruptured, not by the 
elongation of the seta as in the Bryineae, but by the expan- 
sion of the theca of the sporogonium. 
From these facts it appears that Buxbaumia is an ancient 
type of Moss which still retains a number of primitive 
characters. It is also of interest in that it recalls the simplest 
form of the sexual generation of the Ferns. The Hymeno- 
phyllaceae, among the Leptosporangiate Ferns, are forms 
which have a filamentous prothallium on which cellular 
archegoniophores are borne ; the archegoniophore is homo- 
logous with the Moss-plant, since, as has been briefly indicated 
above, the Moss-plant was itself originally only an archegonio- 
phore. In most other Ferns the filamentous stage of the 
prothallium is very brief, because the development of the 
