XII 



LEPTOSPORANGIATA£ HETEROSPOREyE 



405 



and not three, walls. The basal cell of the aichegoniuni in 

 Marsilia divides by cross-walls into equal quadrants, and the 

 lateral cells divide both by vertical and horizontal walls before 

 any further divisions take place in the archegonium. This 

 finally divides into the cover cell and inner cell. The neck is 

 very short, especially in Marsilia, and each row has but two 

 cells. These in Pilulai'ia {¥\g. 211) are much longer. Both 

 neck and ventral canal cells are very small, espcciall)' in 

 Marsilia, and the former has 

 its nucleus undivided. In Mar- 

 silia the prothallium grows 

 gradually as the divisions pro- 

 ceed, but in Pilularia (Fig. 211) 

 the young prothallium increases 

 but little in size until the divi- 

 sions are almost completed, when 

 there is a sudden enlargement. 

 The complete development of 

 the prothallium occupies about 

 twelve to fifteen hours in Mar- 

 silia vestita, and in Pilularia 

 globiilifera forty to forty -five 

 hours. 



The escr in both eenera is 



Fig. 211. — Pilularia glolmlifcra (L.). A, B, 

 Young female prothallia, longitudinal sec- 

 tions, X 300 ; c, neck canal cell ; C, section 

 of a recently fertilised archegonium, X 300 ; 

 sp, spermatozoid within the egg. 



large, but in Marsilia it is the 

 larger. In both, the receptive 

 spot is evident. The nucleus 

 is unusually small in Marsilia, 

 which otherwise resembles 

 Pilularia. 



The phenomena of fecunda- 

 tion are very striking in the 

 Marsiliacese. The mucilagin- 

 ous layer about the macrospore attracts and retains the 

 spermatozoids, which collect by hundreds about it. The 

 mucilage above the archegonium forms a deep funnel, which 

 becomes completely filled with the spermatozoids. 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 confined 

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



