78 BOTANICAL GAZETTE [ FEBRUARY 
clinal division finally separates an exterior primary wall cel 
from an interior primary sporogenous cell. In this latter case 
the tapetal layer is evidently cut off from the sporogenous cell, 
but we have seen that this may occur in other groups as well. 
Such an application of the term archesporium has the meri 
of uniformity and of fairly homologizing its derivatives. It has 
seemed to me that the term tapetum should disappear as a mol 
phological term, inasmuch as it is a physiological layer betweet 
the sporogenous cells within and the sterile cells without, atl 
of variable origin, derived from the wall cells, or from the spo- 
rogenous cells, or from the cells of the adjacent tissue. 
MACROSPORANGIA AND MACROSPORES: 
In the case of R. septentrionalis a single hypodermal cell fre- 
quently represents the whole of the archesporium (jigs. 18-22); 
soon becoming very much larger than the contiguous cells, ant 
with a very conspicuous nucleus. Frequently an axial row a | 
cells beneath this archesporial cell, with prominent nuclei, gives 
the impression of a row of mother cells (figs. 19; 21); = 
the subsequent history of the larger hypodermal cell prove j 
the contrary. In most cases the epidermal cells capping es 4 
single archesporial cell divide once by a periclinal division : 
(Jigs. 20, 23), or occasionally twice, making three layers of cells ' 
but this represents all the development of tissue above * ; 
Sporogenous cells. In this case no primary wall cell (tapetum)® 
derived from the archesporium. | 
In many cases, however, instead of a single archesporial 
a group of cells forms the archesporium. Regarding only bc 
cells which show by their increased size, prominent nuclei, and 
reaction, that they are of undoubted archesporial nature, 
bers varying from two to thirteen were observed (figs. 247" 
In fig. 26 an archesporium of eight cells is shown. +” wnat ; 
cane it was hard to define the archesporium exactly, 45 eels 
contiguous to those of undoubted archesporial nature, by ¥! 
of their size and Seneral appearance, certainly suguese” | 
ea 
sporial character. The evidence is clear that the sing 
