XI 



LEPTOSPORANGIATJE HETEROSPOREJE 



425 



is unusually small in Marsilia, which otherwise resembles 

 Pihdaria. 



The phenomena of fecundation are very striking in the 

 Marsiliaceae. The mucilaginous layer about the macrospore 

 attracts and retains the spermatozoids, which collect by hun- 

 dreds about it. The mucilage above the archegonium forms 



st: 



FIG. 250. Marsilia vestita. Development of the embryo. A, Longitudinal section of 

 archegonium with two-celled embryo; B, similar section of a later stage; C, two 

 transverse sections of a young embryo; D, two longitudinal sections of an older 

 one; I, I, the basal wall; L, cotyledon; st, stem; r, root; F, foot. A-C, X52S; 

 D, 



a deep funnel, which becomes completely filled with the sperma- 

 tozoids. As these die their bodies become much stretched out, 

 so that they look very different from the active ones, with their 

 closely placed coils. The attractive substance here is not con- 

 fined to the material sent out from the open archegonium, as the 



