26 MR. R. H. COMPTON : AN INVESTIGATION OF THE 
members of each pair. The changes which occur in the uppermost 4 mm. of 
the hypocotyl consist in the admixture of the main cotyledon bundles with 
parenchyma, and the gradual passage of the corresponding phloems to a more 
dorsal position (fig. 71). 
Each cotyledon takes a pair of almost collateral bundles derived from the 
metaxylem, and an intervening root protoxylem.  Anastomoses soon take 
place, and this arrangement is quickly lost, a median collateral bundle being 
formed, which forks higher up in the cotyledon. 
GENISTA ZTHNENSIS, DC, 
Moderate-sized shrub. Hypocotyl narrows gradually to a long primary 
root. Cotyledons oblong. 
The two diarch plates persist to 10 mm. above the collet, gradually 
broadening to a wedge-shape. The characteristic T-shape is assumed about 
2 mm. above this, the phloems dividing concurrently; but this lasts a very short 
distance compared with Spartium junceum, the usual triple cotyledon traces 
being organised almost immediately. Thus the transition is much higher than 
in Spartium junceum, and the changes are telescoped. The root and hypocotyl 
appear to be without fibres in the phloem. 
GENISTA HISPANICA, Linn. 
A small shrub. The hypocotyl narrows rather abruptly into the root and 
bears a tuft of rootlets at the collet region. Cotyledons oblong. 
The early stages of the transition occur in the first few millimetres above 
the collet, and the T-shape is early reached by the xylem. This persists 
through the greater part of the hypocotyl, the later stages only taking place 
in the upper few millimetres. The xylem trace consists, as usual, of a pair 
of collateral bundles with endarch spiral xylem and with fibres outside the 
phloem ; between these bundles lie scattered and disorganised root-protoxylem 
elements. 
A good deal of secondary vascular tissue develops early at the collet region, 
this being apparently connected with the tuft of lateral roots. 
CROTALARIA RETUSA, Linn. (РІ. 4. fig. 72.) 
Erect undershrub, reaching 150 em. Hypocotyl somewhat downy. Co- 
tyledons oblong, slightly twisted to one side. Primary root very short, 
a tuft of lateral rootlets arising at the collet region. DeCandolle (1825, 
pl. 6) gives a figure. 
The transition begins 3 mm. below the collet, the two biseriate xylem 
plates broadening to equilateral wedges and then to a V-shape by the 
intrusion of pith (fig. 72), this occurring at the collet; a short distance 
above each breaks into а triad (cf. Pl. 5. fig. 73, for C. incana). 1 em. below 
