402 
FERNS : BRITISH AND FOREIGN. 
I liave at page 65 mentioned that a few intermediate 
forms of the genus Gymnogramma had been raised from 
spores, which are considered sports by some and by 
others hybrids ; the latter can only be admitted on the 
supposition of two Prothallia of two different species 
growing so contiguous to each other that the sperma- 
tozoids of one Prothallium have the power of passing 
and fertilizing the Archegonia of the other, and thus 
produce a hybrid, as in flowering plants. Another 
point of some practical importance is, that in 
general only a single plant bud is formed on each 
Prothallium. This may be supposed to be owing to 
the vital function of the Prothallium not being able to 
support more, in that respect analogous to only one 
ovulum being fertilized in ovaries of many flowering 
plants. Admitting that, then, how are we to explain that 
on removing the plant bud a new bud is formed ; and 
even as many as eight to ten have been obtained from 
Prothallia of Hymenodium cr ini turn, each of which, by 
proper care, becomes a plant. Then again experiments 
have shown, that by dividing the Prothallium from the 
base upwards with a sharp instrument into two or 
even four parts, each part produces a plant bud. 
Seeing this, it is reasonable to infer that Prothallia 
have the power of producing plant buds, analogous to 
leaves of Begonias and other plants ; but whether such 
is the case, or each bud is the result of the action 
of spermatozoids on latent Archegonia, is not known. 
Then again we have the remarkable instance of the 
great profusion of plants produced by the spores of 
all farinose Ferns, such as species of Gymnogramma, 
Cheilanthes, Notholcena, Cincinalis, 8)-c., and also of the 
smooth ebenous genera Pellcea, Platyloma, Doryo- 
