Mitrospermum compressum ( Will .). 
495 
B. The Sarcotesta. 
In the better preserved specimens the shell is enclosed in a delicate 
sarcotesta. This takes the form of a thin layer of tissue clothing the surfaces 
of the valves, and at their lateral edges extending beyond them as a wing or 
flange lying in the principal plane. Sections of the apex of the seed, which 
pass through both shell and sarcotesta exactly in the plane of flattening, 
would be needed in order to demonstrate definitely the contour of the wing 
at the micropylar end. Such sections have not been found, but it is probable 
that the outline in this plane resembled that diagrammatically shown in Text- 
Text-FigURE 2 , A, B, and C. Diagrammatic (slightly restored) transverse sections of Miiro- 
spermum compressum (Will.) (x 8 or 9). a and B are sections from the same seed (slides 1693 
and 1694, in Dr. Scott’s Collection ; from Dulesgate). a is nearer the apex than b. c is a 
section of another seed nearer the base than either a or B (Slide 1417, in the Williamson Collection, 
named in Williamson’s manuscript catalogue Cardiocarpon anomalum). sa. = sarcotesta; sc. = sclero- 
testa; n. = nucellus ; v.b= branch vascular bundle ; w. — wing ; p.p. — principal plane ; s.p.— 
secondary plane ; r. — median ridge of sclerotesta. 
Fig. 1, A. Transverse sections, which seem from internal evidence to have 
been cut near the micropyle, show a greater breadth of wing in proportion 
to the shell than sections taken lower down (cf. Text-Fig. 2, A and c). 
A seed with the sarcotesta preserved, cut through the micropyle in 
a plane at right angles to the plane of flattening (i. e. in the secondary plane), 
fortunately occurs in the University College Collection (PI. XXXVII, Fig. 2). 
It is clear, from this specimen, that the sarcotesta became much thicker at 
the level at which the shell began to taper off to the micropylar orifice. 
The micropyle seems to have been of considerable length, and in the upper 
