=~z 
63 
pylar- and chalazal development occasionally are affected, 
can be traced back to two causes, viz. the shortening of the 
sex-generation and the usual desintegration and final sup- 
pression of non-functioning tissues. Megaspore-formation and 
chalazal development are attacked by both factors, micro- 
pylar development by the first one only. 
. The 8-nucleate sac seems to be the most original type of 
the Angiosperm embryosac. The present study did not suc- 
ceed in throwing any light on its origin. 
