3G4 



ME. F. 0. BOWER ON APOSPORY IN FERNS. 



at various points on the leaves ; these may he ultimately sepa- 

 rated from the parent plant as new individuals of the sporophore 

 generation : as examples may be cited various species of Asple- 

 nium. In the case of the prothallus or oophore generation, a 

 vegetative mode of reproduction by adventitious buds, resulting 

 in the formation of fresh prothalli, has been observed in numerous 

 cases, e. g. Osmunda, Gymnogramme leptophylla, &c* ; and more 

 especially in that form of prothallus described by Cramer, but 

 not identified with certainty : here special gemmce carried on the 

 process of vegetative reproduction of the prothallus f. 



Thus in each of the alternating generations of the Fern the 

 cycle is liable in certain cases to be extended by processes of 

 vegetative reproduction ; this may be represented graphically, as 

 iu the subjoined diagram : — 



Diag. 2. 



Taproductiofv 

 4 



Ytoctativo- 

 ftc production 



Taking now into consideration those modifications of the life- 

 history by which the cycle may be reduced, we may find two 

 points at which a short cut may be taken -.—there may be a 

 transition from the prothallus to the Fern-plant without the 

 intervention of sexual organs ; secondly, there may be a direct 

 transition from the Fern-plant to the prothallus without the 

 intervention of spores. 



^ The former of these short cuts has already been observed: 

 first by Farlow, in Pteris cretica ; and it has been described at 

 length by De Bary + in this plant, and also in other Ferns (Aspi- 



* Goebel, "Entw. des Prothalliums von Gymnogramme leptophylla;' Bot. Zeit. 

 1877; also Goebel, 'Grundziige dor Systematik,' p. 221. 



t Cramer, " Ueber die geschleehtlose Vermebrung des Farnprotballiume," 

 Sep.-Abdr. Denkschr. d. Schweitz. naturforsch. Gesellscb. Bd. xxviii., 1880. 



X Farlow, Quart. Journ. Micr. Sci. 1874, p. 2G6; De Bary, Bot. Zeit. 1878, 

 p. 449. J 



