278 



BOTANY 



prising about eighty species. A third monotypic genus, Loxsoma, 

 is sometimes included in the family. 



Gametophyte. The gametophyte is very different from that of other Ferns, 

 probably due to the excessively moist localities in which they usually grow, 

 which induces an excessive vegetative development, so that sometimes great 



FIG. 245. Trichomanes cyrtotheca. Development of the sporangium (X 225). F, 

 horizontal section of a nearly ripe sporangium ; r, annulus. 



mats of the prothallia are met with, which may easily be mistaken for Liver- 

 worts. In many species of Trichomanes. the prothallium is an extensively 

 branched filamentous growth resembling the protonema of a Moss. In Hymeno- 

 phyllum, it resembles the prothallium of the Polypodiaceae in its earlier stages, 

 and always is flat, but may branch extensively and reach a length of several 

 centimetres. Special gemmse are common in these plants and permit a rapid 



