XXVII] 



GAMETOPHYTE 



245 



may be a thickening ot the margins where the gametangia are produced. 

 Like many epiphytic Liverworts and some other Fern-prothalli there 

 may be a vegetative propagation by gemmae. These are habitually pro- 

 duced in T. alatuvi, venosui/i, and pyxidiferum. They are borne distally, 

 each appearing as a swelling on the tip of a flask-shaped sterigma. 

 Extending laterally, and undergoing segmentation, this forms a spindle- 

 shaped body easily detached, and thereafter it may germinate into a new- 

 filamentous gametophyte (Fig. 517). 



Fig. 516. TricJiofnanes rigiditm Sw. Habit of a 

 prothallus of which only a small part is represented, 

 with archegoniophores [A), on one of which (the 

 lower) an embryo plant is seated. ( x about 50.) 

 (After von Goebel from Engler and Prantl.) 



The gametangia of Trichomanes appear on the ends of dwarf branches 

 (Fig. 518). The antheridia undergo a segmentation similar to that in 

 Leptosporangiate Ferns: by position they closely resemble those of Schizaea. 

 The number of spermatocytes in section (19 in T. pyxidiferum), and the two 

 divisions of the cap-cell (Vol. I, Fig. 283,/") accord with a position between 

 primitive and highly specialised Ferns. The archegoniophore of Trichomanes 

 appears as a short massive lateral branch, bearing a pluralit}- of archegonia 

 of an ordinary type. In Hymenophyllum the antheridia and archegonia ma}- 

 be borne together upon a lateral lobe of the strap-shaped thallus, which may 



