868 TEENS I BRITISH AND FOREIGN. 



I have at page 65 m en tionedthat 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 Arcliegonia of the other, and thus 

 produce a hybrid, as in flowering plants. Another 

 point of some practical importance is, fiat 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 

 ovuluni 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 crinitum>, 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 Arcliegonia, 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, fyc., and also of the 

 smooth ebenous genera Pellcea, Platyloma, Doryo- 



