78 



MORPHOLOGY 



rangia below. There is also a swelling tissue which in this case bursts 

 out at the top of the sporocarp. The remarkable longevity and 

 resisting power of the sporocarps of Marsilea deserve mention. Sporo- 

 carps preserved on herbarium sheets for fifty years and others kept in 

 95 per cent alcohol have resumed activity when placed in water. 



In contrasting the structures called sporocarps in Salviniaceae and 

 Marsileaceae, it is evident that they are very different. In Salviniaceae 



Figs. 412-414. — Male gametophyte of Marsilea: 412, first division of the microspore 

 into vegetative cell (the smaller) and antheridium initial; 413, first division of an- 

 thcridium initial; 414, antheridium with wall of sterile cells investing spermatogenous 

 cells (shaded). — After Campbell. 



the sporocarp is an indusium investing a sorus, while in Marsileaceae 

 it is a leaf blade inclosing a group of sori with their indusia. 



Gametophytes. — The male gametophyte does not emerge from the 

 microspore, as it does in Salviniaceae, remaining entirely within the spore 

 coat, as in Selaginella and Isoetes. As in all the previously mentioned 

 cases of heterospory, a single vegetative cell 

 and a single antheridium make up the male 

 gametophyte (figs. 412-414); but in Marsile- 

 aceae the output of sperms is 32, much larger 

 than in Salviniaceae (8) and in Isoetes (4). The 

 sperms of Marsilea are remarkable for the 

 great number of coils in the beak, reaching 

 13 or 14, the upper 12 or 13 having no cilia 

 (fig. 415). The female gametophyte closely 

 resembles that of the Salviniaceae, and the nucleus of the great nutritive 

 cell remains, undivided, as in Salvinia (figs. 416, 417). 



Embryo. — The embryo develops as in all the leptosporangiate ferns, 

 the first wall of the egg being vertical (parallel with the long axis of the 

 archegonium), and the four body regions being differentiated at the quad- 

 rant stage. It is noteworthy that the Marsileaceae have retained the 

 primary vertical wall of the egg, characteristic of the leptosporangiate 



Fig. 415. — Sperm of Mar- 

 silea. — After Campbell. 



