the Seed in the Alsinoideae. 
49 
from the primary cell itself into this tissue. The function of the suspensor 
as a sucking organ would seem to be limited to the period preceding free- 
cell formation to the endosperm. As the basal cell elongates during the 
growth of the embryo the contents become less dense and more granular, 
and it finally remains as a mere empty sac. 
The endosperm replaces the suspensor as the cotyledons are dif- 
ferentiated in the growing embryo, and we have seen that it is the apical 
portion alone which functions as a secretory organ, in the form of a cap 
composed of a single layer of cells, which invests the radicle. The endo- 
sperm is thus differentiated into two portions, structurally as well as 
functionally diverse — an active apical region, composed of small cells with 
dense contents, and an inactive peripheral portion with large and vacuolated 
cells which are stretched over the remaining surface of the embryo-sac. 
This differentiation is no doubt correlated with the favourable situation of 
the apical portion of the embryo-sac, being in immediate vicinity to the 
perisperm reserves of the nucellus and, through the lower axile cells of the 
latter, to the water supply through the chalaza. 
As the seed matures, we see a further approach to these chief sources 
of food supply by the gradual pressing of the micropyle against the 
chalaza, which is characteristic of the maturation stage. In considering 
the autonomous organization for nutrition in these ovules, it is interesting 
to refer to the complex outside mechanisms in the case of Phlox Drummondi 
(Billings, 24), where in early stages the ovary wall is described as forming 
the starch reserve. A channel for the passage of food supply to the 
embryo is provided in the form of a papillose outgrowth of the ovary 
wall, in the vicinity of the micropyle ; this papilla presses against the latter, 
which becomes closed and serves as conducting tissue. 
The organization of the secretory cells of the endosperm in the 
Alsinoideae is very complete. They form an investing cap surrounding 
the radicle, which grows down into them, and completely fuse with the 
nucellus, forming an intimate connexion between it and the embryo which 
is only ruptured by the elongation of the hypocotyl on the germination of 
the seed. Even then their connexion with the nucellus is not affected, and 
they remain attached to the few strands of tissue which have not been 
absorbed by their agency for the benefit of the embryo sporophyte. In 
some chance sections through a seed, where a fungus mycelium had con- 
sumed the endosperm, evidently not being able to attack the perisperm, the 
embryo was malformed and undeveloped, with two straggling cotyledons 
composed of a few strands of tissue, the whole limited to the apical portion 
of the sac, thus pointing to the endosperm as the one agent for the supply 
of proper food and directive energy. Seeds from which the endosperm 
was artificially removed did not germinate. The results of the present 
investigation, as far as the Alsinoideae group of the Caryophyllaceae are 
E 
