COMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
It is, further, not improbable that the peculiar features of the 
suspensor in some Cruciferae, 0 and many other plants are 
connected with similar physiological conditions. 
The embryo in the Spermacoceae and in Houstonia develops 
very slowly, especially in its early stages. We - have to note here 
the complete absence of the adaptive characters in the suspensor 
seen in the 6۵/2۵۵۵ ; the suspensor is of a very simple structure, 
and upon anatomical evidence alone we might attribute to it only 
the mechanical functions above indicated. In view of the distri- 
bution of food stuffs as already described, however, we must 
recognize the suspensor in these forms as a less special haustorial 
organ than in the Ga/ieae, but still an organ of that nature. 
It may further be noticed that the production of haustoria 
from the suspensor of the embryo, and, so far as known, from no 
other part, is probably an expression of polarity in the embryo. 
8. The endosperm is of two kinds, according to its method of 
development, corresponding to two of Hegelmaier's * types. 
In the Galieae, the endosperm during its whole course of de- 
velopment fills completely the endosperm cavity (Hegelmaier's first 
type) The peripheral cells on the basis of their cytological char- 
acter and the behavior of the adjacent tissues may be regarded as 
concerned in the secretion of an enzyme, and in the absorption of 
the food derived by digestion of the reserve food substances in the 
integument. 
In the Spermacoceae and Houstonia the endosperm is at first 
parietal, later c coming to fill completely the enclosed cavity (Hegel- 
maier's second type). In addition to the peripheral cells, which 
appear much as in the Gadieae, the centrally placed cells in Diodia 
and A/chardsonia take on a more special character with a prob- 
lematical significance. 
THE TETRAD AND EMBRYO-SAC MITOSES 
(PLATES 9 AND 11) ۱ 
The following account of the mitoses of the archesporium and 
of the embryo-sac is based upon a study of Asperula montana, 
Crucianella macrostachya and C. gilanica. Of the two genera, 
* rc über die ee des Dicotyledonen—Endosperms. Nova 
885. 
Acta Akad. Naturforscher., 49 : No. 
