53 
Trigonocarpus Shorensis , sp. nov. 
(PI. V, Fig. 1 6), and in their radial dimension (30-40 p) considerably exceed 
their width (75^-0-025 mm. , average about 0-015 mm.). The central elements 
are polygonal in form and from 0-015 mm * to °‘ o2f mm * diameter. The 
bundle therefore has the appearance in transverse section of a central core 
surrounded by a single layer of radially flattened elements. 
The smallest tracheae, measuring some o-8/x in diameter, lie just within 
this outer layer and appear to form six not very clearly defined groups, two 
corresponding to each of the three angles. That these are the protoxylem 
elements is rendered the more probable by an examination of the single 
longitudinal section passing through the chalazal bundle (S. 32, e). From 
this we find that the majority of the elements were scalariform or densely 
spiral (PI. V, Fig. 18), whilst separated by one such element from the 
periphery of the bundle there appear to be one or two narrow elements 
with distant spiral thickenings. 
The xylem is completely surrounded by a ring of parenchymatous 
tissue (PI. V, Fig. i 6 ,p.s.) composed of three to five layers of thin-walled 
elements which together attain a width of about 0-05 mm. In the longitu- 
dinal section this tissue is seen to have consisted of narrow, vertically 
elongated components, perhaps undifferentiated phloem. The whole bundle, 
including this delicate sheath, was surrounded by larger-celled and thin- 
walled nucellar tissue in which were numerous secretory sacs. One element 
exhibits parallel markings, and may be a transfusion tracheide comparable 
perhaps to those found by Scott and Maslen between the bundles of the 
sarcotesta of T. Parkinsoni (loc. cit., p. 114 and PL XIV, Fig. 25, si.). 
The single bundle passed through the base of the nucellus, where it 
expanded in a cup-like manner and formed a tracheal investment (1-4 
elements) to the megaspore cavity. This is well seen in section D of 
Dr. Scott’s series, which passes obliquely through the base of the megaspore 
cavity, and shows the continuous and several -layered tracheal cup around 
its base. 
As seen in transverse section, the tracheal mantle appears to be built 
up of broad, laterally fused, bands traversing the longitudinal direction 
which are thickest in the middle and gradually diminish towards the sides. 
As can be seen from the plottings (Fig. 1), the section S. 33, c is slightly 
oblique to the axis of the seed, and it is on the higher side of the section 
that this grouping of the tracheides is the more marked. 
Presumably, then, the vascular tissue between the level of this section 
and the base of the megaspore cavity consisted of a uniform zone of 
tracheides, which on the upper side became incompletely segregated into 
bands. The number of these latter cannot be ascertained with certainty, 
owing to the oblique direction of our most nearly transverse sections, but if 
we assume the slight indications of thinning on the lower side to mark the 
lateral limits of vascular aggregations, then there were probably twelve such 
