SEEDLING STRUCTURE IN THE LEGUMINOSAE. 15 
hatching, which supply the first two plumular leaves. The usual pair of 
collateral bundles and median protoxylem are found at the cotyledonary 
node. 
The derivation of this type of structure from the usual Bauhinia type is 
quite clear, the differences being due to the prolongation of the two main 
plumular traces into the root, where they contribute to the metaxylem ; the 
result of their presence being that the two lateral protoxylems on each side, 
which (tracing the process downwards) usually fuse to form the intercotyle- 
donary poles of a tetrarch root, are kept apart and become the lateral poles 
of a hexarch root. This interpretation is borne out by the occurrence of 
seedlings with a tetrarch root, whose lateral xylems separate below the collet 
while the polar xylems are still continuous (fig. 41). 
BAUHINIA : SUMMARY, 
The genus Bauhinia, so far as examined, exhibits certain constant features 
in the transition. The root is typically tetrarch (Pl. 3. fig. 42), but through 
a great part of the hypocotyl six protoxylems are present with eight groups 
of metaxylems, this being brought about by the production of two meta- 
xylem bundles from each root xylem and the division of the lateral proto- 
xylems of the root to accompany their respective metaxylems (fig. 44). The 
hypocotyl of B. racemosa differs from this in the addition of the two main 
plumular bundles, which, being prolonged as metaxylems into the root, keep 
asunder the lateral pairs of protoxylems, so that a hexarch root is the result 
(figs. 38-40). In the upper part of the hypocotyl the stele has a quadrangular 
outline: the cotyledon trace consists of a pair of collateral endarch bundles 
with an isolated median protoxylem (fig. 45). 
Diarchy occurs in the root of B. yunnanensis, and, according to Van Tieghem 
and Douliot, in Cercis: in the former the symmetry becomes tetrarch higher 
up and the transition is normal. 
Phloem-perieycle fibres occur in root and hypocotyl, and also copious 
tannin-sacs. 
The seedlings are usually of considerable diameter ; several show a tendency 
to become hypogeal. The transition is low, even in the comparatively slender 
B. tomentosa. 
CASSIE, 
CERATONIA SILIQUA, Linn. 
A tree 7-10 metres high. Hypocotyl narrows rapidly into a long tap- 
root. Cotyledons ovate. De Candolle (1825, pl. 23) gives a figure of the 
seedling. Dangeard (188%, p. 86) and, later, Tansley and Thomas (1906, 
p, 762) have examined the anatomy of this seedling, and mention that it has a 
iotrarch root and exhibits a low transition, but their detailed results are not 
published. 
