the Seed in the Alsinoideae. 
4i 
finally shrivel and close up (Fig. t 8, i. i.) till in the mature seed the 
mycropyle is so pressed against the hilum that the outer integument 
practically closes over it (PI. VI, Fig. 22). In the young ovule (PI. V, 
Fig. 6, i. i.) the two layers are still distinct, the individual cells composing 
them showing centrally placed and active nuclei. As the ovule increases 
in size they become very much stretched (Fig. 7, i.i), and after fertilization 
the dividing walls are more or less obliterated, the cells lose protoplasmic 
contents, and the nuclei disintegrate, the two layers practically fusing into 
one. (‘ Nahrschicht ’ of Holfert (20).) The inner wall of layer two abutting 
on the nucellus assumes a wavy outline of highly refractive appearance. 
(Pis. V and VI, Figs. 21 and 22, i. i.) This inner wall immediately after 
fertilization becomes cuticularized in conjunction with some of the basal 
layers of the nucellus as already described on p. 36 (Fig. 18 b.c. and i. it). 
Outer integument. This consists also at first of two undifferentiated 
layers (Fig. 6 , 0. i .) but the cells of layer 1 soon increase in size and 
the nuclei drop to the base of the cell (Fig. 7, 0. i. i.). After fertilization 
their walls begin to thicken and grow out but are not cuticularized until 
maturity (Fig. 19, 0. i). They finally form projecting papillae, the surface of 
the walls showing warty projections (Fig. 22, o. i. 1. sec. pap.) or small 
secondary papillae. 
The second layer is composed of small cells with active centrally placed 
nuclei and denser contents (Fig. 7, 0. i. 2). It suggests a transitory proteid 
layer and remains distinct till the embryo is well advanced (Fig. 21, o. i. 2), 
after which the contents gradually disintegrate, the cell-walls become 
crushed against the outer layer and apparently they merely increase 
the mechanical functions of the latter at maturity (Fig. 22, 0. i. 2). (‘ Pig- 
mentschicht ’ of Holfert (20).) The layers of the outer integument contain 
starch even in the germinating seed. Tannin is present in the cells of 
the integuments and the hilum. 
This tannin seems characteristic of the moribund cells of the tegu- 
mentary layers which at maturation are purely protective. 
Balfour ( 27 ) puts forward the suggestion that in non-vascular seeds the 
integuments form the water supply of the ovule. In the case of Stellaria 
media the only possible source of water supply is through the chalaza, the 
integuments being cut off at a very early stage by the cuticularization of 
the inside wall of the inner integument abutting on the nucellus. The base 
of the integuments, however, are in connexion with the chalaza (PL V, Fig. 
12, i. i.), and the possibility of layer 2 of the outer integument forming 
a sort of water jacket to the growing ovule is suggested by the fact that 
in Spergula arvensis the wing which surrounds the ovule in the plane of 
the embryo is formed entirely from the proliferation of the cells of this 
layer (PI. VI, Fig. 23 o.i. 2). These cells contain a little starch, their 
protoplasmic contents are not marked, and the nuclei are small. They 
