1915] MICHELL—STRIGA LUTEA 125 
when the embryo sac has reached maturity, only traces of it are 
to be found lying between the integument and the embryo sac. 
The bulk of the ovule is composed of the thick integument, as 
is often the case in the Scrophulariaceae. Fig. 2 represents a trans- 
verse section through the ovule just above the integument and 
shows the nucleus of the mother cell in synapsis, prior to its first 
division. In the ovule drawn the nucleolus is just visible, but in 
many similar ovules it has disappeared. It was observed that, 
when synapsis occurs, about 1o per cent of the ovules in an ovary 
are in this stage simultaneously. Other stages in the heterotypic 
division were not seen, the next stage being that of the homotypic 
division (fig. 3). Fig. 4 shows the three upper megaspores degen- 
erating, while the fourth has become the embryo sac. 
The development of the embryo sac is perfectly normal. The 
nucleus divides and the resulting nuclei pass one to each pole of 
the embryo sac, the center being occupied by a large vacuole 
(fig. 5). These nuclei divide twice (figs. 6-8), thus giving two 
groups of four nuclei, one at each end of the sac. One nucleus from 
each group then moves toward the center (fig. 9); these two nuclei 
meet and fuse in the upper part of the sac, not far from the egg cell 
(fig. 10). Baticka-Iwanoska (1) found in certain genera of the 
Scrophulariaceae that the polar nuclei fuse about the middle of the 
embryo sac and migrate toward the egg at the time of fertilization. 
SCHMID (13) pointed out that this position of the polar nuclei at the 
time of fusion is not that always found in this family. He found 
that the position at the time of fusion may vary in a single species. 
For instance, in Pedicularis palustris the polar nuclei may fuse in 
the upper, lower, or middle part of the sac. In the cases in which 
fusion occurs in the middle or at the base of the sac, they migrate 
toward the egg at the time of fertilization. 
The synergids have assumed a caplike appearance by the time 
the embryo sac is ready for fertilization. In the embryo sac shown 
in fig. 11 this cap is not yet developed, but the synergids are early 
distinguished from the egg by their much smaller size. In this 
figure the antipodals show signs of disintegration, and at the stage 
a aang in fig. 12 a small deeply staining mass is all that is left 
of them. 
