too Scott and Mas ten. — The Structure of Trigonocarpus . 
thickness with certainty. In the transverse section of the central part of 
the body of the seed shown in PL XI, Fig. 5, the sarcotesta sa at its 
thickest part measures about 2 mm., and there is clear evidence that the 
outer portion, with the exception of the limiting layers /, has been destroyed, 
so that the total thickness would have been considerably more than this, 
at least in the spaces between the ridges of the sclerotesta where it was 
probably thickest. 
In some cases, as in the transverse section figured (PI. XI, Fig. 5), 
the external boundary-line of the sarcotesta follows fairly closely the 
contour of the sclerotesta within, but we are inclined to think that this 
correspondence is not natural, but is merely a result of more or less 
desiccation and compression prior to fossilization, and that the transverse 
section of the whole seed may have been circular. The correspondence 
in outline between the sarcotesta and sclerotesta is seen in several of 
Williamson’s original slides figured in his paper, and his remark that : 
‘ though the external outline of the sarcotesta is less sharply defined than 
that of the endotesta [—our sclerotesta], we yet see that to a considerable 
extent the former follows the latter, the differences seen in the sections 
being due to shrinkage from some collapse in the soft parenchymatous cells 
of the outermost layer,’ 1 seems to imply that Williamson thought the 
correspondence was a natural one. 
The sarcotesta appears to have been thinnest around the body of the 
seed, and to have increased in thickness above and below. This is shown 
in some of the sections figured in this paper. PI. XI, Fig. 3, is a 
transverse section across the base of the same seed as that shown in 
PL XI, Fig. 5. The central mass of dark sclerotic tissue, s. t., continuous 
with the sclerotesta of the body of the seed, is surrounded by a well- 
developed sarcotestal tissue, which in places is quite 3 mm. thick, and in its 
natural condition must have been much thicker than this, as a considerable 
loss of tissue is indicated by the remains of disorganized cells, as well as by 
the doubling in of the limiting layers of the sarcotesta, /. PL XI, Fig. 1, 
is another transverse section of the same seed, but taken still lower : the 
inner part of the sarcotesta is preserved, but great loss of tissue is shown 
by the limiting layers which are in places doubled in and repeated four or 
five times. 
Passing to the upper end of the seed, a transverse section across the 
lower part of the micropylar beak is shown in PL XI, Fig. 7, and it will 
be seen that the sarcotesta sa is here quite well-developed, as indeed it 
continues to be right up to the end of this organ. 
The sarcotesta consists typically of thin-walled parenchyma without 
special peculiarities. The inner portion is compact and consists of cells 
without visible inter-cellular spaces. In the body of the seed, these thin- 
1 Williamson (’ 77 ), p. 250. 
