Scott and Mas ten . — The Structure of Trigonocarpus . 99 
No pollen-grains are present in the pollen-chamber of any of the specimens 
which we have examined. 
Within the nucellus, and separated from it by a space, is the mega- 
spore membrane (PI. XI, Pig. 5, in.), which in all our slides is preserved 
merely as a line without visible structure. No prothallium or archegonia 
are preserved. 
The vascular supply to the seed consists of two sets of bundles, which 
are given off at different levels from the main bundle. The supply strand 
which enters the base of the seed, while still at a considerable distance 
below the base of the nucellus, gives off a number of bundles (probably 
six) which traverse the sarcotesta of the seed, lying opposite to some of the 
smaller (secondary) ridges of the sclerotesta. These sarcotestal bundles are 
embedded in the inner denser tissue of the sarcotesta, and were evidently 
complete bundles with phloem as well as xylem, although the former has 
not been preserved. From the best preserved examples it appears probable 
that the xylem was of mesarch structure, the smaller, protoxylem elements 
occupying an internal position. 
The second vascular system of the seed runs in the nucellus and is 
rather complex in its arrangement. It springs from the upper end of the 
main bundle which spreads out in the lower part of the seed, and forms 
what appears to be a practically continuous sheath of tracheides, comparable 
with the tracheal mantle of a Stephanospermnm 1 . Transverse sections 
across the central part of the body of the seed show that the tracheides 
range themselves in more or less definite and crowded longitudinal strands, 
which are connected by transverse anastomoses running in a tangential 
direction. The nucellar vascular system has been traced through the 
whole length of the nucellus almost to the base of the pollen-chamber, and 
indications of possible tracheides have been detected even in the beak of 
the pollen-chamber itself. 
The Testa . 
The Otiter Coat or Sarcotesta. The outer thin-walled layer of the 
seed-coat is usually either destroyed altogether, or is represented by only 
a few layers of cells, immediately external to the dark-coloured inner layer 
or sclerotesta. Externally the cells representing the sarcotesta usually 
have no definite limiting layer, while internally the junction with the 
sclerotesta is a sharp one, especially in transverse sections across the body 
of the seed. In good specimens, however, the sarcotesta is better preserved, 
and is then found to be a tissue of considerable extent, limited externally 
by well-differentiated epidermal and hypodermal layers (PL XI, Figs. 5, 6). 
The sarcotesta is never completely preserved, but is always more or less 
collapsed and disorganized, so that it is not possible to estimate its original 
1 Oliver (’04) (i), p. 363. 
