TO BrrRp’s-EYE FORMATION IN THE WOOD OF TREES. 29 
particles adhering to the root in Plate XI., Fig. 4o are held 
there by those hairs. The behaviour of the roots when grown in 
water agreed exactly with what might have been expected, that 
is, they became very much elongated, with no vestige of root- 
hairs and assumed the white colour typical of water-roots. Two 
or three roots of a cutting were kept just above the level of the 
water, with the result that they did not undergo the same change 
in character as those which were submerged. 
THE STEM.—In a radial longitudinal section which has passed 
through a bud of the young stem the centre is occupied by a 
relatively broad pith, bounded on either side by a narrow white 
strip of young wood, from which the leaf-trace-bundles may be 
seen to come off and to pass upwards in an oblique direction 
through the cortex each on its way toa leaf. If, after a leaf has 
fallen, the scar left be examined, three dark dots may be seen on 
its surface, which indicate that three leaf-trace-bundles enter 
the petole; although only one is seen in a longitudinal section. 
The vascular system of the axillary bud is also seen to come 
off from that of the mother-axis, but at a much higher level than 
the leaf-trace-bundles. 
The sequence in which those various branches come off from 
the main system may readily be made out in transverse sections. 
In a section which passes across the main axis just at the place 
where the leaf-traces come off we have three outstanding bundles 
—a large central one and two smaller laterals which are about to 
pass through the cortex on their way out to a leaf-base. A 
section taken a little higher up shows that the lateral leaf-traces 
pass quicker into the cortex and become free sooner than the 
central one. In a section taken still higher up, and which passes 
through the base of the leaf-cushion, all three traces have become 
quite independent strands. The vascular system of the bud 
comes off here, interior to but in the same radial plane as the 
central leaf-trace. The cambium ring of the stem passes in a 
loop-like manner round its periphery, and the pith is also con- 
tinued out into it. This semi-circular portion of cambium 
proceeds to lay down xylem on the inside and phloem on the 
outside. Further up, when the vascular-system of the bud with 
its central pith becomes entirely free, this cambium forms a 
complete ring. This arrangement of the leaf-trace and bud- 
