494 
Tans ley and Lulham. — A Study of the 
gutters (hooks in vertical section of the node) attached to the bases of 
the backward curls. After the backward curls have become continuous 
with the compensation-tongue (roof of the second cylinder) and the 
gap is formed in the second cylinder, the outer limbs of these gutters are 
left attached to the free edges of this gap, and are continued forward for 
some distance as flanges, ultimately dying away before the gap in the second 
Fig. ii. Side view of vascular system of node of large tricyclic form. The side of the outer 
(first) cylinder and base of the leaf-trace towards the observer is cut away, exposing the left lateral 
loop of the leaf-trace. Outer cylinder with uniform shading. Middle cylinder together with lateral 
loops of leaf-trace, compensation-tongue, and mid-dorsal strip of outer cylinder in front of node, 
i. e. parts supplied from middle cylinder, cross-hatched outside, dotted inside. Inner cylinder with 
mid-dorsal strip of middle cylinder in front of node, black outside, white inside. The middle cylinder 
is represented as if transparent, so that inner cylinder is seen through it. a-a. upper cut edge, 
b-b. lower cut edge of outer cylinder, b. 1. t. back, s. I, t. side of main arch of leaf-trace ; 
i. 1 . 1 . inner limbs, o. 1 . 1 . outer limbs of lateral loops of leaf-trace ; f. flanges on edges of gap 
in middle cylinder, forming the forward continuations of o. 1. 1. ; c. t. compensation-tongue passing 
upwards and forwards from middle cylinder attached to bases of lateral loops, and behind cut edge 
of outer cylinder, to foim mid-dorsal strip of outer cylinder ; g 1 , g 2 , g' , gaps in outer, middle, and inner 
cylinders respectively. The arrows indicate the direction of the protoxylem-channels of the left 
lateral loop. 
cylinder is closed (Plate XXXIII, Figs. 30, 31, and Text-Fig. 11). A study 
of the course of the tracheids shows that they run up from the side 
of the second stele and back along these flanges into the forward curls of 
the trace, while the existence of continuous protoxylems in these flanges 
and gutters (p. 508) shows that this water-channel is laid down early, 
and is presumably well established and important in the economy of 
this most complicated type of vascular system. 
Again, the leaf-gap (i. e. the space between the backward curls of 
the trace) is considerably wider, and hence the gap left in the second 
