Scott and Maslen . — The Structure of T rigonocarpus. 1 1 3 
parenchyma to that seen surrounding the bundle in the higher section 
shown in PI. XI, Fig. 4 } a. 
PL XI, Fig. 3, is a transverse section probably cut quite close to the 
base of the body of the seed, or across the upper part of the stalk, of the 
same specimen as that illustrated in Figs. 1 and 2. The central core 
of sclerotic tissue, s.t., continuous with the hard coat of the body of the 
seed, is well seen, as also the gradual transition of this tissue into the 
surrounding sarcotesta with the characteristic bounding layers, /. The 
main vascular bundle, b., is just discernible occupying a sub-central 
position in the sclerotesta, while in the surrounding sarcotesta six bun- 
dles, s.b., can be seen. The outer part of the sarcotesta has been destroyed, 
with the exception of the external layers, /., which are pressed in on 
the more durable tissues. 
The central sclerotic tissue is produced on one side, probably owing to 
the section being somewhat oblique, so that it passes across the lower 
portion of one of the principal longitudinal ridges of the body of the seed. 
As before mentioned no sarcotestal bundle is seen opposite to the point of 
this projection, although two are seen occupying a fairly symmetrical 
position opposite to its sides. The bundle and surrounding tissues of 
PI. XI, Fig. 3, are represented magnified about 100 times in PI. XI, 
Fig. 4. The magnification of Figs. 2 and 4 is equal, so that the bundle 
at the two levels may be directly compared. In Fig. 4 the main supply 
bundle, b., is shown, and appears to have a diameter of about -14 mm., or is 
about half the size of the bundle of Fig. 2 cut at the lower level. The 
larger size of the bundle in Fig. 2 favours the view which has been already 
expressed, that in this section the sarcotestal bundles had not yet been given 
off, as the section is below the level of branching. 
Returning to the section shown in Fig. 4, no clear evidence of 
a differentiated phloem surrounding the xylem can be made out, but 
the bundle is embedded in a comparatively large-celled, apparently paren- 
chymatous tissue, which occupies the space within the core of hard tissue. 
It will be noticed that the triangular form is still preserved to a certain extent, 
though it is not as sharply marked as in the lower section (PL XI, Fig. 2). 
In all probability the main supply bundle was concentric in structure. 
A definite protoxylem cannot be made out in this transverse section, 
and, unfortunately, the longitudinal sections which show the main bundle are 
not sufficiently good to help us in this matter. Miss Stopes has shown 
that in Cycads : ‘ The main supply bundle is usually either completely 
concentric or has a strong tendency in that direction ; the bundles given off 
to the outer flesh are collateral and orientated with the phloem outwards, 
and with a considerable development of centripetal xylem ; the strand con- 
tinuing to supply the inner system has a strong concentric tendency 1 .’ In 
1 Stopes (’ 05 ), p. 560. 
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