I4I0 



A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 1 30 1. — Hypericum mysorense. A, Four-nuclear stage of endosperm development, 

 showing starch grains surrounding nuclei. B, Sixteen-nuclear stage, with most of 

 the starch around the chalazal nucleus. C, Chalazal coenocytic cyst with abundant 

 starch. D, The same from nearly mature seed, showing the disappearance of starch. 

 {After Sivamy.) 



of rectangular cells, which we have previously described as the ovular tape- 

 turn or endothelium. This has a restrictive action on the expansion of the 

 sac, which remains narrowly cylindrical and only expands, if at all, at the 

 micropylar and sometimes also at the chalazal ends, where it has grown 

 beyond the cuticularized barrier layer. The epidermis of the nucellus is 

 also generally cuticularized and this thin cuticle remains around the sac 

 even after the nucellus has been destroyed. It is, however, usually dissolved 

 at the micropylar end, so that it offers no barrier to penetration by the pollen 

 tube. 



