



1917] 



WENIGER— EUPHORBIA 



271 



ment of the cyathium agrees with that given by Miss Lyon (8) for 



E. corolla ta. 



Embryo sac 



/), which soon becomes an 



integuments 



formed in each locule of the ovary. Before the 

 to appear, the megaspore mother cell can be distinguished by the 

 size of its nucleus (figs. 5, 11). It is subepidermal in origin and 

 larger than the surrounding cells of the nucellus. After increasing 



m 



formation of a typical 



(fig. 13), of which 



innermost 



the embryo sac. 



inner integument 



outer (oi), which appears a little later, grows the more rapidly. It 

 has been stated by Poisson (16), working on E. Lathyrus and 

 E. Peplis, and by Schweiger (20), investigating many species of 

 Euphorbia, that the outer integument develops before the inner- 

 It would be easy to arrive at a similar conclusion in the case of 

 E. Preslii, since one rarely obtains a preparation showing the stage 

 at which the inner integument is appearing at the base of the 

 nucellus before any trace of the outer is to be seen, and since the 

 outer integument grows so rapidly that it very early extends 

 beyond the inner. In all probability, closer study of this species 

 would show that in these also the inner integument begins its 

 development first, as is the case in E. corollata, E. Preslii, and 



* 



E. splendens. 



At the time of the first nuclear division in the functional mega- 

 spore, the outer integument reaches about half-way to the tip of the 



the inner integument is still extremely 

 integument begins to grow more rap 



As 



welling 



Its 



increase 



and slender and giving to the structure 

 The nucellus grows out into a long beak 

 beyond the integuments. At this time 

 sac has reached the 8-nucleate stage, and 



fills the snnre hptwppn thp hpaklikp. nrnl 





