— 158 — 



into the chalaza outside the nucellus. In H. excellens the origin of this 

 ES was a cell quite near the tetrad. In the following development 



of both ES one can 

 observe just such a 

 competition as in 

 H. excellens. Fig. VII 

 shows three diffe- 

 rent stages in the 

 development of an 

 \jl \ \\\ aposporic ES. 



As regards the 

 other species I will 

 only speak in brief 

 as the examination 

 is not yet complete. 

 K i r c h n e r (8) poin- 

 ted out that in H. 

 aurantiacum the egg 

 cell became an em- 

 bryo without ferti- 

 lization. I have 

 found that ES here 

 is nearly always of 

 aposporic origin. It 

 begins to form very 

 early, simultane- 

 ously with the tetrad 

 division , and its 

 origin is most com- 

 monly an epidermic 

 cell of the nucellus 

 which encroacheson 

 the tetrad (Fig. VIII). 

 This often occurs 

 so early that it is 

 difficult to deter- 

 mine the value of the ES. A careful investigation, however, shows 

 that nearly always the typical ES becomes quite crushed or often 

 cut off by the aposporic ES. It is therefore always necessary to 



13 



Fig. VII. H. flagellare, aposporic embryo sac formation. 



