258 BOTANICAL GAZETTE [APRIL 
the archesporial cells dividing in various planes, and blending 
indistinguishably. The sporangium is single, not multiple, and 
the megaspore mother cells are not morphologically predeter- 
mined but are physiologically selected from among a large num- 
ber of potentially sporogenous cells. 
Though the certainty of the matter must depend upon 
observation, it may be pointed out that the number of mega- 
spores has a bearing upon the question. A megasporangium 
contains from 150 to 250 megaspores. If we take 200 as the 
average, it represents fifty mother cells, that is, according to the 
current view, fifty archesporial cells. To this we must add at 
least fifty others for the trabeculz, giving a total of one hundred 
archesporial cells. It does not need a very careful examination 
of /. echinospora to demonstrate the impossibility of there being 
so large an archesporium, for when the sporangium has a super- 
ficies of one hundred cells it is far past the archesporial stage. 
It is, I think, absolutely certain that each archesporial cell gives 
rise to several megaspore mother cells, as well as to trabeculae 
and tapetum. In the microsporangium, too, the trabeculz alone 
outnumber the archesporial cells (cf. figs. 31, 46); and their 
extreme irregularity and frequent branching and anastomosis 
make their origin each froma single cell exceedingly improbable. 
[ To be concluded. | 
