51 MR. R. H. COMPTON : AN INVESTIGATION OF THE 
Each cotyledon double xylem bundle carries with it a pair of phloem 
groups with fibres, these having arisen from the halves of the adjoining root 
phioems. The remaining halves on the side of the axis away from the 
cotyledons move tangentially and fuse in the intercotyledonary plane over 
the first-leaf trace. Before departure each cotyledonary phloem bundle gives 
off another branch inwards (Pl. 9. fig. 99). The branches between the coty- 
ledons divide into several groups : the innermost fuse in the intercotyledonary 
plane and become the median phloem of the second-leaf trace: the two 
outermost attach themselves to small groups of xylem given off from the 
neighbouring metaxylem group, and pass up into the epicotyl as the cortical 
fibrovaseular bundles: the intermediate pair increase much in size and 
become lateral phloem bundles of tho epicotyl. The branches on the side 
away from the cotyledons suffer no further division but become lateral 
bundles of the epicotyl also (fig. 100). 
Meanwhile the protoxylem of the second-leaf trace appears at the node, 
being inserted on the same side as the cotyledons. Its exact position may 
vary. In one instance it was seen to appear in a position external to the 
intercotyledonary metaxylem, and to move inwards gradually until it became 
continuous with, and on the inner side of, the metaxylem (figs. 99-101). In 
other cases it originated in the position it finally occupied. 
The metaxylems now suffer a rearrangement: the one in the inter- 
cotyledonary plane bends round the end of the ellipse (tig. 101) and breaks 
into two lateral bundles, the other two remaining in the same position. 
Then the xylem on each side of the ellipse fuses into a long band (fig. 102) 
and the two bands become compressed towards the major axis, where they 
fuse and obliterate the pith. A central mass of xylem is thus produced some 
few mm. up the epicotyl (fig. 103). 
The median bundle of the first leaf gives off a fibre bundle, which breaks 
through the (still dotted) endodermis, and places itself in the cortex ; shortly 
afterwards the second-leaf trace does the same (fig. 102). 
About half-way up the epicotyledonary internode, therefore, we find the 
usual four cortical bundles, two fibrous and two fibrovascular : and within 
the endodermis two polar fibrovascular bundles, a central dumb-bell-shaped 
mass of xylem, and four lateral groups of phloem with fibres * (fig. 103). 
At the departure of the first leaf (a trifid bract) the median leaf trace 
passes out and joins the cortical fibre bundle; simultaneously each cortical 
fibrovascular bundle gives off a branch which becomes a lateral strand of the 
* Hérail (1885, p. 219) calls the fibres pericyclic, but the point is ditlieult to determine. No 
“typical” phloem intervenes between them and the parenchymatous pericycle: two layers 
of the latter lie between the central fibres and the endodermis, 7, e. the same amount as lies 
between the “typical " phloem and the endodermis. 
The xylem of the first-leaf trace has a double appearazce, not shared by the phloem ; this. 
reflecting its origin from one of the root xylem poles (ef. Cesalpinia sepiaria). 
