424 



MOSSES AND FERNS 



CHAP. 



off first from the papilla. In Pilularia the next wall is parallel 

 to this transverse primary wall, and this may also occur in 

 Marsilia, but in the latter more commonly the first lateral cell 

 is first cut off by a vertical wall, and this is followed by two 

 others, which intersect it and include a large central cell (Fig. 

 248, E), from which a basal cell is subsequently separated. In 

 Pihdaria, besides the formation of the basal cell by the second 

 wall, the central cell is, as a rule, cut out by two, and not three, 

 walls. The basal cell of the archegonium in Marsilia divides 



by cross-walls into equal quad- 

 rants, and the lateral cells divide 

 both by vertical and horizontal 

 walls before any further divi- 

 sions take place in the arche- 

 gonium. 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 Pihilaria 

 (Fig. 249) are much longer. 

 Both neck and ventral canal cells 

 are very small, especially in Mar- 

 silia, and the former has its nu- 

 cleus undivided. In Marsilia 

 the prothallium grows gradually 

 as the divisions proceed, but in 

 Pilularia (Fig. 249) the young 

 prothallium increases but little in 

 size until the divisions are almost 

 ¥io. 2^9.-Piiuiaria giohuUfera A, B, completed, whcu thcrc is a sud- 



Young lemale protnallia, longitu- '- 



dinai section, X300; c, neck canal dcu enlargement. The complete 



cell; C, section of a recently fer- deVClopmCnt of the prOthalHum 



tilised archegonium, X300; sp, / ■*- 



spermatozoid within the egg. OCCUpicS about tWClve tO fifteen 



hours in Marsilia vestita, and in 

 Pilularia giohuUfera forty to forty-five hours. 



Coker (i ) states that in Marsilia Drummondii the nucleus 

 in the basal part of the spore subsequently becomes very large 

 and irregular in form and finally divides amitotically in several 

 parts which apparently remain active for some time. 



The egg in both genera is large, but in Marsilia it is the 

 larger. In both, the receptive spot is evident. The nucleus 



