16 



mopiPttoloitY of sperjiatopiiytes 



The first indication of a megasporana'inm is the differentia- 

 tion of a gronp of sj-Kirogenons cells innnediatelv beneath the 

 epidermis. It is not a liypodernial jilate. as in the niicrosporan- 

 ginni, bnt a hypodernial mass of c<:>nsideralile extent. AVhether 

 this gronp represents the archesporiTun, or whether it can be 

 traced hack to a few-celled or even to a one-celled arcliesporinm, 

 is still in donbt. Our impression is that there is a many-celled 

 archesporimn. Following tlie dift'erentiation of sporogenous 

 tissne, the exterior sterile cells begin to divide rajjidly, organ- 

 izing the large sterile apical region of the nncellns. About this 

 there develops a very thick integnnient ^vith a long and narrow 

 micropyle. 



By means of this development of the exterior sterile tissne 

 the sporogenous tissue becomes deeply placed in the nucellns, 



Fig. 13,_/;/„,,„ ct/ii/t, si'ctioiuil vu'W ol' ^ll■Ml.il^|s ivpivsriitud in Fio-. I'J 



a]-.].earing alniust at its very base. Tu the sporogen.Mis tissue 

 nsually one cmtrally -|ila<-ed cell shows its selection for func- 

 tioning by enlarging at the expense of adjacent cells. From its 

 .subsc(|n(Mit liehavior it seems that this eidargino- cell is the 



