308 



MOSSES AND FERNS 



CHAP. 



tached. In this way, as well as by the separation of ordinary 

 branches, the prothallia of some species of Hymenophyllum 

 form dense mats several inches in diameter, which look exactly 

 like a delicate Liverwort. A most remarkable case is that of 

 Ano gramme leptophylla, examined by Goebel ( i ) . The pro- 

 thallium multiplies extensively by buds, some of which form 

 tuber-like resting bodies, by which the prothallium becomes 

 perennial. The sporophyte in this species is annual and dies as 

 soon as the spores ripen. The archegonia are borne on special 

 branches of the prothallium, which penetrate into the ground 

 and lose their chlorophyll. Goebel ((10) p. 245) suggests 



B. 



FIG. 171. A, Prothallium of Pteris cretica, with the sporophyte, sp, arising as a veg- 

 etative bud; B, apex of the root of Asplenium esculentum, developing into a leafy 

 shoot. (A, after De Bary; B, after Rostowzew.) 



what seems very probable, that the subterranean prothallium 

 of the Ophioglossacege may be of this nature, and the fact that 

 in Botrychium Virginianum the germinating spore develops 

 chlorophyll would point to this. 



Apogamy and Apospory 



Apogamy, or the development of the sporophyte from the 

 prothallium as a vegetative bud, was first discovered by Farlow 

 (i) and later investigated by De Bary (2), Leitgeb (13), and 

 Sadebeck (6). It is known at present in Pteris Cretica, As- 



