38 MR. R. H. COMPTON : AN INVESTIGATION OF THE 
There does not seem, however, to be the same tendency for the proto- and 
metaxylems to become detached from one another ; nor are fibres so strongly 
developed in the phloem. 
Lorus cornicuatos, Linn. (РІ. 1. fig. 17.) 
Hypocotyl passes smoothly into the primary root, which quiekly forks. 
Cotyledons ovate, shortly petiolate. 
The xylem of the root is in the form of a solid threc-rayed star of small 
size. The phloem contains no fibres. No change in structure occurs until 
about 5 mm. below the cotyledons. Here a pith begins to appear: two of 
the xylem rays increase their angular distance and the phloem between them 
divides into two groups. ‘Ihe polar xylems eventually become almost opposite ; 
the third (lateral) xylem gradually dwindles and finally becomes almost 
extinct. No trace of a fourth protoxylem was detected. The cotyledonary 
trace at the node consists of two small tangential groups of metaxylem with 
protoxylem between, and of two groups of phloem lying laterally to the 
metaxylems. The final stages of the transition are accomplished just above 
the first branching of the cotyledon veins. 
Lotus corniculatus has recently been examined by Chauveaud (1911, p. 351), 
who gives a figure of a transverse section at the base of the cotyledon and a 
description of the transition phenomena. 
Doryenium HIRSUTUM, Sér. (Pl. 6. figs. 87-89.) 
Small bushy plant. Cotyledons ovate, articulated to the short petiole. 
The structure of the lower part of the hypocotyl and root is very variable. 
Out of ten seedlings examined two were found to have a tetrarch root, five a 
triarch, and three a diarch. The upper part of the hypocotyl, however, shows 
the same structure, whatever the symmetry of the root. 
(i.) The xylem in a tetrarch root consists of four equal biseriate plates of 
vessels meeting in the centre of the stele. This arrangement continues till 
nearly half-way up the hypocotyl. A small pith then appears and the 
xylems in the cotyledonary plane are separated somewhat: as the pith. 
increases the lateral xylems broaden out tangentially, and at the same time 
their protoxylems become compressed towards the centre. The stele thus. 
becomes elliptical, and the lateral protoxylems lose in importance relatively 
to the polar: the latter remain narrowly wedge-shaped and conspicuously 
exareh. The xylem remains in a continuous ring round the pith to within 
2 mm. of the cotyledons : then a separation into two cotyledonary traces takes. 
place (fig. 89) ; and the narrow V-shaped xylems (each composed of a polar 
group and a pair of attached half-laterals with their protoxylems) quickly 
collect into the usual type of double bundles. 
The exareh position of the polar protoxylem continues into the base of 
the cotyledons, and the pair of phloem bundles are in a tangential position. 
