142 



PRINCIPLES OF PLANT-TERATOLOGY. 



kind may be represented in fig. 40, where the tissue 

 of the pinnule gradually merges into that of the pro- 

 thallus, a case which reminds one of the adventitious 

 shoots of Neottia, etc., terminal to the root and a 

 direct continuation of its apex, as also of the forma- 

 tion of adventitious shoots in ferns as a direct out- 

 growth of the leaf -apex. In Trichomanes the prothalli 

 arose directly from the pinnule in a similar way. Also 

 Druery observed, in Nephrodium .pseudo-mas and Sco- 

 lopendrium vulgar e var. Drummondm, the formation of 



Fig. 40. — Scolopendrium vulgare var. Drummondse. Portion of frond 

 showing incipient prothalli formed aposporously. (After Druery.) 

 pr, prothallus. 



prothalli on the margins of the frond (fig. 40). It 

 may be mentioned that in some of these prothalli 

 sexual organs occurred. 



Another phenomenon must here be referred to. 

 Just as the sporophyte may give rise to other sporo- 

 phytes adventitiously on its leaves, in the same way 

 the oophyte or prothallus may produce secondary 

 prothalli adventitiously. Cramer observed this in 

 Osmunda and Gloebel in Gymnogramme ; in the latter 

 they may be formed marginally or on the surface, as 

 the result of injury to the apex of the normal pro- 

 thallus, or in the absence thereof. Treub observed 

 the same phenomenon in the prothallus of Lycopodium. 



