﻿BOTANICAL GAZETTE 



primary endosperm nucleus has already divided, and thus there is 

 no means of detecting whether a male nucleus took part in its forma- 

 tion or not. This early stage in endosperm formation is shown in 

 fig. 4, where the antipodals are still distinct. 



Sterile ovules 



Gow (7) has reported that in Richardia as observed in the Cedar 

 Rapids greenhouses, a large number of ovules are congenitally 

 sterile, producing no embryo sac. In my South African material 

 this does not seem to be the case. In a few ovules no functional 

 embryo sacs were found, but judging from the fact that a group of 

 degenerate cells could be distinguished in the nucellus in each case, 

 it seems probable that an embryo sac had oeen formed and had 

 collapsed. 



Development of the embryo 



Owing to the fact that fertilization had occurred in very few 

 cases, ovules showing young embryos were only occasionally found. 

 Endosperm development precedes that of the embryo, and by the 

 time the small spherical embryo consists of 32 cells, the embryo sac 

 is filled with endosperm. 



In one case a 2-celled structure, which had every appearance 

 of being an embryo, had developed at the chalazal end of the embryo 

 sac (fig. 15a). Its protoplasm is fine and dense, making a marked 

 contrast with the coarsely granular protoplasm around the endo- 

 sperm nuclei which are found in the next section (fig. 15*)- The 

 position of the antipodals is indicated by the degenerating cells 

 shown in figs. 15a and 156. This was the only case in which an 

 embryo was found in any but the normal position, and its origin 

 is not known. In this embryo sac an egg was organized (fig- 

 although it has evidently not been fertilized. 



In all the other ovules the proembryos seen had at least 32 cells 

 and were spherical in shape. Fig. 16 shows a somewhat oblique 

 M < turn passing through an embryo with over 3 2 cells. The embryo 

 conforms to the type described by both Campbell and Gow for 

 the Araceae. 



