358 GoebeL~On the Simplest Form of Moss . 
archegoniophore begins early. The prothallia of species of 
Trichomanes present forms which resemble the sexual genera- 
tion of Buxbaumia ; and the prothallium of Trichomanes 
sinuatum , which I found in British Guiana, connects in the 
most striking manner these prothallia with those of typical 
form. 
It seems to me that an accurate comparative consideration 
of the sexual generation of Ferns and of Mosses leads to 
establish on a firmer basis the homologies which have been 
detected between them. With regard to the asexual genera- 
tion of these two great series of Archegoniata, it appears that 
the prevailing view which regards it as following from the 
very beginning an altogether different course of development 
in each series still continues to hold good, however desirable it 
may be to establish more detailed homologies between them. 
Attempts in this direction have not been wanting, the most 
recent being that of Bower 1 , which is based on elaborate 
investigations. Bower attaches special significance to the 
‘sterilisation of tissue’ in the sporangia. There can be no 
doubt that such a sterilisation actually takes place, as it also 
does in a striking manner in the Moss-sporogonium ; but it is 
a question how far this may proceed in sporangia and sporo- 
phylls. My earlier researches showed that the trabeculae of 
the sporangium of Isoetes are the result of partial sterilisation 
of the sporogenous tissue ; but I would only attach a biological, 
that is, an adaptive, significance to the fact. The sporangia of 
Isoetes are especially large and bulky, and therefore require 
considerable quantities of nourishment for their development ; 
the trabeculae are doubtless the channels by which nourish- 
ment is conveyed to the sporogenous tissue, just as is the case 
in the sporogonium of certain Liverworts. Again, the horse- 
shoe-shape curvature of the sporangia of Lycopodium clavatum 
has, in my opinion, merely the object of bringing the sporo- 
genous tissue into direct relation with as large a surface as 
1 Bower, Studies in the Morphology of Spore-producing Members ; Proc. Roy. 
Soc., vol. 50 : also paper read before the Edinburgh meeting of the British 
Association, 1892. 
