444. ALDEN: LIFE HISTORY OF UVULARIA SESSILIFOLIA 
suggest an enlarging hypodermal cell at the side next the carpel 
wall, ric. 11. The cells of the hypodermal layer, however, do 
not show the characteristics of the usual archesporial tissue, for 
the cells are only slightly enlarged, the cytoplasm not dense, and 
the chromatic network not prominent. Moreover, more than one 
of the hypodermal cells show a slight increase in size, perhaps 
indicating the archesporial potentiality of several hypodermal cells, 
FIG. 12. This is indicative of a primitive condition. A single 
cell, however, increases more rapidly than the others, getting a 
start over the others, for in the material of March 14 this greater 
increase is noted in the cell destined to develop the embryo sac, 
FIG. 13. 
By the first of April this enlarging cell has become quite promi- 
nent, giving the cell mass a decidedly one-sided appearance. 
The nucleus is large but still with inconspicuous reticulum. This 
cell continues to increase in size, FIG. 14, and toward the end of 
April projects strongly, and the inner integument has begun to 
develop. The nucleus at this stage shows synapsis, indicating 
that the hypodermal cell does not divide to cut off a primary wall 
cell but functions directly as the megaspore mother cell, FIG. 15- 
Five days later, April 30, the turning of the ovule, which was 
slight on April 25, is now almost complete and the ovule typically 
anatropous. The integuments have grown rapidly and almost 
surround the embryo sac. Owing to the twisting of the ovule at 
this time, it has been found difficult to obtain a longitudinal 
section of the developing mother cell. However, in material 
collected May 7 the division of the mother cell, which was !? 
synapsis one week earlier, is complete, and two cells, which may 
be called megaspores, are seen. Vesque’ has stated that each 
develops an embryo sac to the four-nucleate stage. 
SUMMARY 
1. The archesporium of the microsporangium, 
from 3 to 6 hypodermal cells, becomes differentiated 
of August. : 
2. The hypodermal cells divide at this time forming the ee 
mary sporogenous and the primary parietal cells. ne 
3. The primary parietal cells divide several times, giving S€ 
to the permanent wall of the sporangium and to the tapetum. 
consisting of 
the first 
