344 BOTANICAL GAZETTE [NOVEMBER 
THE DEVELOPMENT OF THE MICROSPORANGIUM. 
To trace the development of the anther, and especially the 
differentiation of the microsporangial archesporium in Pota- 
mogeton, is no less difficult than in Convallaria. Oddly enough, 
the only monocotyledonous type studied by Warming was one 
of the Naiadacez, namely Zannichellia. Warming thought that 
in this plant the process was essentially identical with that in 
the dicotyledons, but these results may be questioned, owing to 
the apparent paucity of material at his command. 
The present study of Potamogeton seems to throw a little 
more light on the problem. In the young anther, which at 
maturity is always two-celled, there is found at each of the two 
more prominent angles of the quadrangular cross-section a single 
hypodermal cell, which at this stage is slightly larger than the 
surrounding cells and richer in protoplasm. This presently is 
divided by periclinal walls into two, and later into three daughter 
cells, each produced probably in centrifugal succession (jig. 25). 
The innermost of this series now immediately begins to enlarge, 
and becomes at once the primary archesporial cell. This cell 
undergoes rapid division, resulting at length in a number of cells, 
all formed from this one original archesporial cell. The irregu- 
larity in arrangement, and the gradual decrease in size from the 
center toward all sides, nevertheless suggest that some may owe 
their origin to the division of the surrounding tissue. The 
same gradual decrease in size takes place also on the side of the 
archesporium toward the connective. 
It will be seen from the above account that the tapetum here 
and in Convallaria is not a morphologically distinct structure 
until at a comparatively late period in the development of the 
anther. It is not until the stamen is half mature that the arche- 
sporium becomes distinct from the wall. It can always be gat 
nized at this period by the finely granular contents of the = C 
just as was the case in Convallaria. No tapetum can be ae 
guished for some time. The cells of the inner layer of the wall, 
which from the first are smaller than the central cells, ace 
‘take on a dense and partially disorganized appearance. There 
