VAILLANTIA HISPIDA 15 
mass is coördinately reduced, while the basal antipodal shows its 
maximum development during this period. The probe-like end, 
which, I believe, serves as a haustorium, at this time and some- 
what later is filled with cytoplasm which appears finely reticulate, 
while the broad end which is adjacent to the upper part of the em- 
bryo-sac is occupied by a large vacuole. This large antipodal 
must, therefore, stand in an important relation between the food 
supply derived from the archesporium and the endosperm cell, 
and is probably active in the transportation of the food from the 
former to the latter. The megaspore mass thus forms a sort of 
nutritive tissue, partly analogous to that described by Dr. Balicka- 
Iwanowska (/ c.) as occurring in the region of the integument 
near the lower ends of the embryo-sac in the forms studied by 
her. 
The archesporial tissue is now seen to bear a nutritive rela- 
tion to the embryo-sac, which by this time has reached maturity. 
THE DEFINITIVE EMBRYO-SAC 
We may now pause to sum up the characters of the mature 
embryo-sac. E 
In shape it is fusiform and much attenuated at the lower end. 
The upper part, comprising one third or more of the entire length, 
contains the egg apparatus and the endosperm nucleus, and consti- 
tutes the expanded part of the embryo-sac. The fusion of the 
polar nuclei takes place at about the middle of this part of the 
embryo-sac, but at the time of fertilization the resultant nucleus 
comes to lie immediately against and partly surrounding the egg 
nucleus. The migration of the endosperm nucleus has been no- 
ticed by Mme. Balicka-Iwanowska (l. c.) in Digitalis and other 
related forms in which the embryo-sac is more or less attenuate. 
At the time it reaches the egg, the nucleolus has nearly three 
times its original diameter. Its size relative to that of the egg 
nucleus is shown in Pl. 2, Fig. 8a. The nucleus itself is larger 
than the egg nucleus, but the discrepancy in size is more striking 
between the nucleoli. This movement and growth of the endo- 
sperm nucleus must be interpreted physiologically ; it is in all 
probability in some way connected with the nutrition of the egg. 
The antipodals are three in number; two of these are small 
