126 Scott and Maslen . — The Structure of Trigonocarpus. 
no trace of an annular ridge. That the three processes shown in PI. XIII, 
Fig. 20, r., r., r., are only longitudinal ridges is also made clear by their 
absence in the more radial section of the upper part of the same seed shown 
in PI. XIII, Fig. 19. 
PI. XIII, Fig. 2i, is a vertical tangential section, and shows the cavity 
of the seed, c., and the surrounding sclerotesta, s.t. The sclerotesta is much 
thicker on one side than on the other, probably because the section passes 
through one of the longitudinal ridges on that side. On the thicker side 
a nearly detached portion of the sclerotesta is shown, probably correspond- 
ing to another longitudinal ridge. 
PI. XIII, Fig. 22, is still more tangential, as it shows little more than 
the sclerotesta, s.t., with a trace of the cavity of the seed within. The 
sharply pointed upper and lower ends of this section probably indicate 
that the section passes through one of the longitudinal ridges, and that 
these had very acute edges. In Trigonocarpus Parkinsoni the ridges were 
more blunt or round, and none of the numerous sections which we have 
examined of this form are at all like the section shown in PI. XIII, Fig. 22. 
We do not think that the form represented in this figure is a possible one 
for Trigonocarpus P arkinsoni. 
The innermost cells of the sclerotesta, especially in the section shown 
in Fig. 22, have dark contents and are quite different from the rest of 
the cells of this layer. They are continued as fine lines from the centre 
of the section (Fig. 22) through the middle of the longitudinal ridge shown 
above and below. The splitting of the testa along the ridges, which can be 
seen in Figs. 20 and 22, appears to proceed along these cells, which seem to 
be in a state of disorganization. In this form the splitting of the testa 
along the ridges would thus appear to have been a natural process corre- 
lated with the presence of special cells occupying the central parts of the 
sclerotestal ridges. 
The presence of a circular ridge surrounding the base of the seed, 
and enclosing, presumably, the stalk by which it was attached to the parent 
plant, is a character which Trigonocarpus Oliveri possesses in common with 
Polylophospermum stephanense , a French seed which has been recently 
re-described by Professor Oliver h Indeed longitudinal sections of the base 
of this seed compare closely with similar sections of Trigonocarpus Oliveri. 
PolylophospermMn stephanense is a long prismatic seed, hexagonal in 
transverse section and prominently ribbed along the salient angles, while 
both at the apex and base there are cup-shaped incurved outgrowths of the 
testa which produce two false chambers at the ends of the seed. One of 
these chambers encloses the micropylar beak, and the other the stalk of the 
seed. The length of this seed is about 1-5 cm., or somewhat less than that 
of Trigonocarpus Oliveri. 
1 Oliver (’04) ( 2 ). 
