the Seed in the Aisinoideae. 
47 
the outgrowth of the nucellus best, it cuts into the cells of the outer integu- 
ment on the posterior side of the ovule. 
Conclusions. 
The general result of work done on the Caryophyllaceae, section 
Aisinoideae, emphasizes the view that it is a very well-defined group of 
plants, the members being characterized by great uniformity both in the 
morphological development of the sporophyte and in histological structure. 
This uniformity extends to the reproductive organs, and investigation on 
the Aisinoideae in this direction tends to show that apart from more 
specific differentiation there is a certain developmental trend in the direc- 
tion of greater specialization from the Sperguleae to the Alsineae. 
If we pass in review the results obtained, the three most important 
points seem to be — 1, the organization of the ovule in relation to the 
passage and storage of food supplies for the embryo ; 2, the manner in 
which such food supplies are rendered available ; and 3, the indication of 
certain lines along which development has proceeded within the group. 
1. The organization of the ovule. The ovule in its complete form con- 
sists of the chalaza, a large nucellus with embryo-sac, invested by two 
integuments, and each of these component parts stands in important 
relation to the development of the whole. 
The chalaza is the seat of elaboration of proteid material, and the 
whole of the organized food supplies required for the growth of the ovule 
and embryo, together with water and air, must pass through this tissue. 
It is situated in a very advantageous position, abutting on the vascular 
system of the funicle which branches freely into it during the later stages 
of development, whilst on the distal side its cells are in serial connexion 
with the axile rows of the nucellus. The perisperm is laid down in the 
upper region of these axile rows. Laterally, the chalaza is in communica- 
tion with the integuments. The medium of diffusion between the chalaza 
and the nucellus would appear to be a few of the basal layers of the 
nucellus, the walls of which become cuticularized after fertilization and 
show shallow pits. In the mature seed and on germination large air spaces 
occur in the angles formed by the walls of several layers of the unmodified 
nucellar cells immediately above the cuticularized layers. This fact is 
suggestive of a possible function for these basal layers as a species of 
aerenchyma. That all gaseous interchange must necessarily be limited to 
this ‘ aerenchyma * is shown by the early cuticularization of the inner wall 
of layer 2 of the inner integument which effectually cuts off every other 
source of supply. 
The immediate elongation of the embryo-sac which follows closely on 
fertilization, and its subsequent enlargement in the vicinity of the chalaza, is 
