18 MR. R. H. COMPTON : AN INVESTIGATION OF THE 
9:5 mm. at the collet to 1:0 mm. at the cotyledonary node; narrows rapidly 
to a slender root. Cotyledons ovate. 
Only one seedling was obtained, and this was probably somewhat smaller 
than normal. The transition was of the intermediate-low type found in 
Cassia spp., the details of structure closely resembling those described for 
C. levigata. The distension of the base of the hypocotyl involves the cortex 
only, the stele not being proportionately enlarged. 
Pith appears about 3 mm. below the collet ; triad-formation is achieved at 
about a quarter of the way up the hypocotyl ; fusion of metaxylems, division 
of lateral protoxylems, and the organisation of the cotyledon traces occur in 
the upper quarter of the hypocotyl. 
PETALOSTYLIS LABICHEOIDES, /0. Dr. 
Hypocotyl tapering upwards in a remarkable manner (cf. Labichea lanceo- 
lata), and contracting sharply to the root; a prominent serrate collar is 
developed at the collet. Cotyledons ovate. 
The transition is exceptional among the Czesalpinioidez, in that it is high. 
The root contains a small tetrarch stele with four equal 2-seriate xylem plates 
meeting at the centre. These separate slightly from one another just above 
the collet, but throughout the lower three-quarters of the hypocotyl four 
exarch xylem-wedges are found, the whole aspect of a section being root-like. 
The contrast at the collet between the broad cortex and the narrow stele is 
striking. 
About 3 mm. below the cotyledons the xylems become distinctly double, 
consisting of paired irregular groups of metaxylem with mesarch proto- 
xylems. The lateral xylems divide about this level and join the polar groups, 
so that each cotyledon receives a pair of xylem bands with a median polar 
protoxylem and two groups of phloem. The transition is incomplete at the 
node. 
Clearly the distension at the base of the hypocotyl does not affect the 
transition phenomena of this essentially slender seedling. (Cf. Labichea 
lanceolata, Kennedya retusa, ќе.) 
EU-CZESALPINIE.E. 
PARKINSONIA ACULEATA, Linn. 
Shrub or small tree. Hypocotyl with prominent collar at base, below 
which it tapers rapidly to a long root. Cotyledons ovate, thin. Figured by 
De Candolle (1825, pl. 22). 
The root has a pith throughout: it contains a continuous ring of primary 
xylem with four projecting protoxylems. This ring breaks into four 
tangential bands, each with a median protoxylem just below the collet ; the 
amount of xylem is reduced gradually as we ascend, and triads are produced 
