BEITISH MOSSES. 21 



knowledge, the different parts in the cycle of the life- 

 history of the Moss may be expressed by other terms than 

 those of alternative generations, and some larger generaliza- 

 tion may be arrived at which will remove the difficulties 

 which seem to stand in the way of the received doctrine. 



One observation must be made to correct the generality 

 of some of the language I have already used. I have 

 spoken of the growth from the spore of the Mosses as 

 a thread-like protonema : that from the spore of the ferns 

 as a prothallus. This statement is generally but not 

 universally true. The true Musci always, so far as is 

 known, produce a protonema. The sphagnum produces 

 protonema when the spore develops in water, but a pro- 

 thallus when on the ground : the Hepatic produce some- 

 times a protonema, sometimes a flat plate of cells, or a 

 mass of tissue. On the other hand, in the Ferns, whilst 

 the ordinary first produce of the spore is a prothallus, in 

 the filmy ferns, this is, so far as has been observed, a 

 thread-like protonema closely resembling the like structure 

 in Mosses. These facts show an approximation between 

 the two great groups of cryptogams, the Ferns and the 

 Mosses, and may hint to us the possibility of some direct 

 genetic relation between them. 



Modes of reproduction. The remaining columns of the 

 foregoing table B are epitomes of other modes of repro- 

 duction than the one which we have already described. 



Hitherto our whole attention has been addressed to the 

 reproduction from a spore produced in the special organ 

 for their production the spore capsule. But so far is 

 this from being the only form of generation, that, in fact, 



