REDUCTION OF THE GAMOBIUM 



365 



sporangium, by sending out a filament the end of which (spy) 

 becomes separated off by a septum and then divided into 

 two cells. The protoplasm of each of these divides into 



. mi 



-rm.sp 



FlG. 86. Reproduction and Development of Salvinia. 



A, portion of a submerged leaf, showing three sori in vertical section, 

 two containing microsporangia (mi. spg) and one megasporangia (nig. 

 spg). (X 10.) 



B, a germinating microspore (mi. spg), showing the vestigial prothallus 

 (prlh) and spermary (spy). (X 150.) 



C, diagrammatic vertical section of a germinating megaspore, showing 

 the outer (mg. sp) and inner (mg. sp') coats of the spore, and its cavity 

 (c) containing plastic products, separated by a septum (</) from the pro- 

 thallus (prth), in which two ovaries (ovy) are shown, that to the left 

 containing an ovum, that to the right a polyplast. (X 50. ) 



D, megaspore (mg. sp) with prothallus (prtJi) and phyllula just begin- 

 ning to develop into the leafy plant : sf, stem ; ct, cotyledon ; and /, 

 outermost leaf of the terminal bud. (X 20. ) 



(A and B, after Sachs ; D, after Pringsheim.) 



four sperm-mother-cells, and from these spirally-twisted 

 sperms are produced in the usual manner. It is obvious 

 that the two cells in which the sperms are developed repre- 

 sent a greatly simplified spermary : the single proximal cell 



