422 



MOSSES AND FERNS 



CHAP. 



blepharoplast increases in size, and shows several granular 

 bodies within it, and it is from these granules that the cilia- 

 bearing band is developed. 



The blepharoplast becomes much elongated and with the 

 nucleus moves toward one side of the sperm cell (Fig. 247, D). 

 The nucleus also elongates, but the blepharoplast extends far 

 beyond it. The blepharoplast finally forms a funnel-shaped 

 coil of ten or more turns, of w^hich the three posterior coils, 

 which are much wider, are in contact with the slender coiled 

 nucleus, which does not extend beyond this point. (Fig. 247, E). 



The Macrospore and Female Prothallium 



The macrospores of the Marsiliaceae are extremely complex 

 in structure, and are borne singly in the sporangia. In Mar- 



FlG. 247. — Marsilia vestita. Development of the spermatozoid, X1500. A-C, lasd 

 division preliminary to the formation of the spermatids; D-F, development of the 

 spermatozoid; n, nucleus of spermatid; b, blepharoplast (after Shaw). 



silia vestita they are ellipsoidal cells about .425X.750 mm. in 

 diameter, ivory-white in colour, and covered with a shiny muci- 

 laginous coating. The upper part of the spore has a hemi- 

 spherical protuberance covered with a brown membrane, and 

 it is the protoplasm within this papilla that forms the prothal- 

 lium. The apex of the papilla shows the three radiating ridges 

 like those in the microspores, and indicates that, like them, the 

 macrospore is of the radial or tetrahedral type. 



Sections of the ungerminated spore (Fig. 248, A) show a 

 structure much like that of the microspore, but more highly 



