216 



PTERIDOPHYTA. 



Sexual generation. The MICROSTORES produce an extremely 

 rudimentary prothallinm, formed of only a single cell, and having 



A B C D 



FIG. 214. Sal"inia nntntis : A microsporan^ium with germinating mierospores and pro- 

 truding prothaUia (s) ; B a prothallium with thebicellular antheridium (s) growing out of 

 the Tnicrosporangium ; C the two cells of the antheridium have opened by transvetse 

 clefts ; beneath is seen the mierospores enclosed by the hardened mucilage ; D spermato- 

 zoids still enclosed in the mother-cells. 



tiiso a very much reduced bicellnlar antheridium with a small 

 number of spermatozoid mother-cells in each cell (in Salvinia 4, in 

 Marsilia and Pilnlaria 16). In Salvinia the mierospores remain 

 embedded in a hard mucilaginous mass (at first frothy) which fills 

 up the cavity of the sporangium. The prothallium must therefore 



A 



B 



-So/em ri ,,,il,,s. A, B Female prcthallia,/-/, protruding frcm the maerosprre 

 11 end scd in the maprosporangii.m; a; archegonin. C An embryo (x 10) 

 H connection with tl.r spm-e (s) : the scutiform leaf; ?>- the subsequent foliage- 

 B, ..I which V and o stand singly, ,7-e-r in a whnrl ; r the submerged-leaf ; /-/wing- 

 like lobes of the prothallium ; m the foot. 



