ASPERULA 37 
the ovule, especially of the integument, is such that the upper part 
of the sporogenous tissue becomes compressed so that the indivi- 
dual cells become displaced and distorted to such a degree that 
the whole appears almost abnormal. This appearance is accen- 
tuated during and after the division of the mother-cells, which, it 
would seem, is by no means as regular as in Crucianclla. This 
irregularity is most striking in Asperula montana, in the ovule of 
which plant the compression appears to be greatest on the micro- 
pylar part of the archesporium. This condition is obviously the 
cause also of certain curious abnormalities in the behavior of the 
embryo-sac to be described shortly. The irregularities in the be- 
havior of the archesporial tissue consist in the differences in rapid- 
ity with which tetrad formation takes place, in the partial or total 
suppression of tetrad formation in a greater proportion of the mega- 
spores, in the early destruction, by pressure, of some of the cells, 
and finally are such that the accurate observation of the behavior 
of individual cells is rendered almost impossible. 
That tetrad formation takes place normally, however, is quite 
sure, from the fact that, in spite of the confusion, rows of four cells 
each are repeatedly found. The megaspores, sister to the func- 
tional embryo-sac cell, persist in apparently normal condition for a 
period at least equal to that occupied by the development of the 
embryo-sac, and occupy, forasmuch as they do not secrete cell 
walls, the same cavity as the embryo-sac. It sometimes happens, 
too, that they have quite the appearance of the antipodal cells, so 
that it becomes difficult to distinguish between them. 
After the functional embryo-sac cell has started to migrate 
(pl. 8, fig. 2), some of the other megaspores persist, while others 
degenerate. Some, further, secrete cell walls, and undergo changes 
which indicate that they are passing through early stages of em- 
bryo-sac development. One such cell is shown in the upper right- 
hand part of the figure. 
It seems equally certain that the tendency is for the upper of 
the tetrads to become the embryo-sac. The pressure already 
referred to, however, modifies the ordinary mode of procedure, so 
that not only may some other of the megaspores rather than the 
upper become the embryo-sac, but it may also be forced to develop 
in quite the wrong direction. This is the case in Asperula mon- 
