the Seed in the Alsinoideae. 
37 
layer two of the inner integument (i. i. Text-fig. 4), the walls of the latter 
also becoming cuticularized (PI. V, Fig. 18, b. c,). In a longitudinal section 
through the chalaza and base of nucellus (Fig. 12, b. c .) these cell layers 
are shown between the small polygonal cells of the chalaza and the 
rectangular layers of the nucellus. Their continuity with layer two, of the 
inner integument, can also be traced. The walls of these basal cells show 
pores, which do not occur on the cuticularized walls of the inner integu- 
ment. These pores probably allow the free passage of water, for in these 
ovules the vascular tissue of the funicle does not penetrate beyond the 
chalaza (Figs. 18, 19, v. b.) y and there is no vascular system in the nucellus 
or integuments. Nawaschin ( 22 ) figures a cuticularized area of thickened 
cells in the chalazal region of the elm ovule, which suggest comparison 
with the basal cells described above for the Alsinoideae. No further 
explanation is offered in the text. 
Godfrin ( 15 ) notes that orthotropous and campylotropous ovules vary 
only in the nucellus being straight or curved. In both cases the hilum 
is directly under the nucellus and, with few exceptions, the seeds are 
non-vascular. Though he does not explain the fact, possibly the ad- 
vantageous position of the chalaza, or hilum in the mature seed, has 
something to do with the efficient distribution of water, without the 
supplementary aid of a branching vascular system. The fact that as 
the ovules mature the terminal vessels of the funicle branch freely in the 
chalazal tissue may be adduced in support of this view (Figs. 18, 19, v. b .). 
The reserve food material is laid down directly over this the sole source 
of water supply, the cuticularization of the inner integument after fertiliza- 
tion, as described above, effectively cutting off all other channels. 
In the mature seed and on germination large air spaces occur in 
the angles of the walls of the first two or three layers of the axile nucellar 
cells immediately above the cuticularized basal cells, which suggest the 
possibility of these latter cells forming a sort of aerenchyma (PI. VI, Figs. 
22 and 24, a . s.). 
Perisperm. Before fertilization starch is limited to the layer of nucellar 
cells adjoining the embryo-sac (PI. V, Figs. 6, 7, st.), the axile cells of the nu- 
cellus being as yet undifferentiated in respect of size and contents. After 
fertilization, however, starch is laid down very actively in those axile cells 
which immediately abut on the embryo-sac ( prm . Text-fig. 4), and in this 
way the process of development of the perisperm is inaugurated in the 
nucellus (PI. V, Figs. 16 and 38, prm). Progressive development of the 
perisperm occurs (Pis. V and VI, Figs. 19, 22 ,prm.) until it forms a tongue 
of cells so densely packed with starch grains that the nuclei are squeezed 
out of all shape, but as the base of the nucellus, towards the chalaza, is 
approached, the starch contents become less and less, the cells are much 
smaller, the nuclei more and more active and the cytoplasm denser in 
