SEEDLING STRUCTURE IN THE LEGUMINOSA, 33 
the root 2 em. below the collet was found to be triarch, but in this case also 
the condition changed to one of tetrarchy 5 mm. below the collet (fig. 78). 
Chaveaud (1911, p. 352) also finds a high transition in this species, and 
gives a figure of the vascular structure at the base of the cotyledon. 
TRIGONELLA CRETICA, Boiss. (Pl. 1. fig. 3.) 
Erect annual herb. Hypocotyl tapering slowly to the long little-branched 
primary root. Cotyledon rather thick ; lamina obovate, jointed to a short 
petiole ; short cotyledonary tube. 
The transition phenomena are almost identical with those exhibited by 
Medicago lupulina, both in the change from tri- to tetrarchy and in the level 
and conformation of the transitional structures. 
TRIFOLIUM ARVENSE, Linn. (Pl. 1. fig. 15.) 
Hypocotyl passing smoothly into the primary root. Cotyledons ovate, 
jointed to short petiole : short one-sided eotyledonary tube. 
The transition is closely similar to that in Medicago lupulina. The change 
from triarchy to tetrarehy takes place in some instances 1 or 2 mm. below 
the collet, in others not till about 2 mm. above the collet. The changes have, 
however, not quite advanced so far at the node as in M. lupulina., 
TRIFOLIUM HYBRIDUM, Linn. 
Hypocotyl tapering slowly toa long primary root. Cotyledons ovate, jointed 
to short petiole. The smallest seedling studied. 
The root is triarch, the number of vessels being very small (about ten). 
This structure persists about half-way up the hypocotyl ; a small pith then 
appears, and shortly afterwards a fourth protoxylem in the intercotyledonary 
plane. Thus at three-quarters of the way up the hypocotyl we have a tiny 
pith surrounded by a continuous ring of xylem with four protoxylems ; four 
phloems alternate with the latter. The whole vascular system then divides 
in half along the minor axis, the V-shaped halves after slight rearrangement 
entering the cotyledons. 
MEDICAGO LUPULINA, Linn. (РІ. B. figs. 79-81.) 
A procumbent much-branched annual or biennial herb. The hypocotyl 
narrows slowly to a long and little-branched primary root. Cotyledons ovate, 
moderately thick, green, spreading just above the ground. (PL 1. fig. 1.) 
The root is triarch (fig. 79) ; the three equal 1-2-seriate xylem plates 
meet in the centre of the stele. The phloems contain groups of thick-walled 
fibres which abut externally on the single-layered parenchymatous pericycle. 
The endodermis is large-celled, with dots on the radial walls. 
At the region of the collet one of the three xvlem plates becomes a little 
weaker than the other two, and the latter increase their angular distance from 
120° to 180° (fig. 80). At the same time the phloem between them elongates 
LINN. JOURN.—BOTANY, VOL. XLT. D 
