the Seed in the Alsinoideae , 
33 
Miss Lister ( 19 ) notes the spongy nature of the septa in this group, 
and suggests their probable function as conducting- tissue for the pollen- 
tubes. In the course of the present investigation, tubes were repeatedly 
seen in the septa of the ovary, and also penetrating through the papillae 
which clothe their surface, to the micropyles of the ovules. These papillae 
persist after fertilization, and, as the septa break down as the ovules increase 
in size, the ruptured surface on the columella becomes covered by similar 
outgrowths of the cells. They evidently serve to ensure the nutrition, and 
form the conducting-tissue for the pollen-tubes in their passage to the 
ovules. In Arenaria tenuifolia these papillae elongate considerably, entirely 
filling up the cavity of the ovary. They replace to a certain degree the 
septa, all of which become broken down by the growth of the ovules, and 
possibly they may serve as paraphyses to keep the ovules damp. 
As the pollen-tube makes its way through the conducting-tissues of 
the style and septum of the ovary to the ovule, some modifications take 
place in the latter. The contents of the fan-like rows of cells forming the 
extreme apex of the nucellus, as previously described on p. 31, show 
increased density and darker staining properties, and the terminal cells of 
these rows grow out as long papillae into the micropyle (Fig. 13, ap. nuc .). 
The inner integument projects far beyond the outer, and the cells of 
which this projecting portion is composed show considerable increase in 
size and darker staining properties (Fig. 7, i. it). The contents of these cells 
are used up by the growing pollen-tube, the walls shrink, leaving a cavity, 
and it is this cavity that the papillose outgrowths of the nucellar apical 
layers project. 
The function of these cells is probably to ensure the nutrition, and to 
facilitate the passage, of the pollen-tube to the embryo-sac. Their subse- 
quent absorption by the pollen-tube leaves a channel from the apex of the 
nucellus to the embryo-sac, in which the tube persists for a long time 
(PL V, Figs. 1 7 and 18, p. t). 
Before entering the synergidae the pollen-tube forms a slight swelling, 
and the apex then forces its way between them and lies against the oosphere 
(Fig. 9, p. t.\ Further penetration into the cavity of the embryo-sac was 
not observed. The pollen-tube in all other species of the Alsinoideae 
examined is very thick and persistent, forming a very characteristic twist 
on itself before penetrating the synergidae (Figs. 13, 17, p. t). But Stellaria 
media forms an exception to this rule. Tulasne ( 5 ), in his drawings of 
dissections of the embryo-sac with suspensor and embryo, figures the twist 
adhering to the apex of the embryo-sac in every other species examined by 
him, and he lays stress on the fact that it was impossible to dissect out the 
one without the other. In Stellaria media , however, this was not the case, 
and he found it difficult to isolate an embryo-sac with the pollen-tube still 
in contact, the latter remaining in the micropylar region and in the apical 
D 
