50 MR. R. H. COMPTON: AN INVESTIGATION OF THE 
halves of the fourth root protoxylem, itself never produced, The transition 
is completed on the tetrareh plan: each cotyledon takes a triad of bundles 
which gives off lateral veins directly it enters the cotyledon. 
The structure is thus similar to that of Coronilla montana, but shows the 
origin of the “fourth” half-xylems rather more clearly. 
HEDYSARUM coronariumM, Linn. (РІ. 8. figs. 96, 97.) 
Hypocotyl broadens upwards, and is somewhat compressed and flattened 
by the persistent pericarp. Cotyledons orbicular, much turned to one side, 
inserted on broad tube, pinninerved. The first two leaves are alternate, and 
not, as De Candolle states (1825, p. 100), opposite, though the internodes are 
very short. De Candolle (1825, pl. 14) and Lubbock (1892, p. 432) give figures. 
The root is triarch, containing three equal 1-2-seriate xylem plates, and 
having fibres in the phloem. The xylem increases in bulk as we enter the 
hypocotyl, and half-way up the third (intercotyledonary) xylem divides in 
two, the opposite phloem doing the same (fig. 96). By the broadening of 
the polar xylems and the junction with them of the half-laterals, a pair of 
double bundles is produced: these being of the ordinary type save for the 
presence of the lateral protoxylems on one edge of each, the collateral 
bundle to which it is attached being markedly larger than its fellow. In 
this eondition the bundles which have come up from the root enter the broad 
cotyledonary tube. As the tube becomes free, however, a minute collateral 
bundle appears de novo on the side opposite to that of the third xylem; this 
bundle promptly divides into two similar halves (fig. 97), which speedily 
separate from one another and anastomose with the double bundles. Tt is 
quite elear that this new bundle represents a fourth root xylem, whose 
appearance is here delayed until the cotyledonary tube is free from the axis. 
ONOBRYCHIS SATIVA, Lam. (РІ. 1. fig. 4.) 
A perennial herb, with woody root-stock and stout ascending stems. The 
hypocotyl quickly narrows to the root, being sharply constricted at the collet 
region by the valves of the persistent fruit. The cotyledons are oblong-ovate, 
slightly secund, one edge being curved more than the other, moderately 
thick. 
The root xylem is triarch and the phloem contains fibres. The first 
changes occur in the region of dilation at the external collet. The xylems 
spread out internally and soon assume a tangential position, the edges of 
adjacent metaxylems uniting to form a continuous ring round the small pith. 
As we ascend into the hypocotyl the pith dilates, but the xylem ring remains 
closed. In the hypocotyl a gradual increase of the pith occurs at the 
expense of the cortex. The three xylem groups become distinct, and 
ove of them divides into two parts, which go to join the other (polar) xylem 
groups on their way to the cotyledons. These latter xylems never become 
