SEEDLING STRUCTURE IN THE LEGUMINOSA. 25 
outside the xylem arms (fig. 68). The V-shape of the xylem persists into the 
base of the short cotyledon-tube, with but little modification. In the base of 
the cotyledons the protoxylem changes its position somewhat, and the xylem 
double bundle becomes mesarch. Finally, just before the branching of the 
cotyledon midrib, the xylem becomes completely endarch and the phloems 
fuse dorsally over а single median metaxylem bundle ; thus the transition is 
coinpleted. 
THERMOPSIS MONTANA, Nutt. (РІ. 4. figs. 61, 68.) 
Hypocotyl tapering gradually to a long primary root. Cotyledons ovate, 
asymmetrical, one edge being almost straight, rather fleshy. 
The features of the transition are almost identical with those described for 
Baptisia leucantha, but the changes take place at lower levels; the transition 
being best designated “intermediate.” Broadening of the diarch 1-2-seriate 
xylem plate occurs below the collet; and at the collet a pith is present, the 
xylems being Y-shaped. Half-way up the hypocotyl the metaxylems are 
practically tangential, with half-phloems almost superposed (fig. 68). 
GENISTEÆ. 
SPARTIUM JUNCEUM, Linn. (Pl. 4. figs. 69-71.) 
A switeh plant with long narrow green woody stems, which are leafless 
except in moist conditions of life. Cotyledons ovate, with scarcely any tube. 
The whole seedling is rather firm in consistency. 
The root (fig. 69) is diarch, containing massive primary xylems, not 
meeting at the centre, consisting of 2-3 rows of reticulate vessels and fibres 
with thick and strongly-staining walls. Each phloem contains a band of 
strong fibres. Тһе endodermis is strongly dotted, the lignifications persisting 
three-quarters of the way up the hypocotyl. 
Practically no change occurs below the collet. Just above, however, the 
xylems separate somewhat, and broadening internally become wedge-shaped, 
this gradually changing into a characteristic T-shape, the protoxylem lying 
externally to the metaxylem arms of the T (fig. 70). The phloem fibres die 
out in the hypocotyl ; the phloem divides concurrently with changes in the 
xylem, so that each T-shaped xylem has a pair of phloems extending from 
the angles between protoxylem and metaxylem towards the intercotyledonary 
plane. This condition persists through the greater part of the hypocotyl. 
About 5 mm. below the cotyledons each xylem splits into three groups—an 
effete median protoxylem and two strong lateral metaxylems, whose vessels 
are now chiefly spiral instead of pitted. These metaxylems move outwards 
slightly, through the dilation of the pith at the expense of the cortex ; so that 
the root protoxylem comes to lie between but somewhat exterior to the 
