659 
certain Orders of the Ranales. 
mentioned outlying ones, pass into them ; by further division and enlargement 
of the strands at the corners of the cylinder the wings become well supplied 
with bundles, all orientated as those on the dorsal side of the cylinder, while 
all the time the original cylinder of the petiole is maintained, and the pith 
becomes narrower and narrower. Eventually the pith becomesobliterated, 
and the ventral bundles of the cylinder pass across and fuse with those of 
the dorsal side, some of the smallest ones dying out in situ ; the same thing 
occurs with the bundles of the wings, until finally a wide-sheathing base, 
enclosing the stem at the node, is formed. There is nothing special to 
narrate about the mode of union of the petiolar bundles with the stem- 
cylinder. 
Aerial stem : In spite of the wide hollow pith, the scattered arrange- 
ment of the bundles prevails here in marked form in the comparatively 
narrow zone allotted to the vascular tissue, the three ranks of bundles 
being very independent as regards their relative positions. The xylem is 
very V-shaped and the phloem pronouncedly circular. A well-marked 
sclerotic zone surrounds the cylinder (PL XXXII, Figs. 9-21). 
I will consider two more plants before leaving the Ranunculaceae, viz. 
Hellehorus and Clematis , as they show some points of interest. 
Helleborus odorus , Waldst. & Kit. 
Leaf : The ordinary horseshoe-shaped arc prevails in the petiole with 
a narrow gap on the ventral side. In the sub-divisions of the lamina, 
however, the inverted ventral bundles occur in various positions, and are 
fairly numerous ; some very small ones lie closely contiguous to the ventral 
face of an arc-bundle (Fig. 7). Another one lies rather obliquely on the 
ventral side and some distance from the arc. I regard them as representing 
a vestige of the primitive cylinder. 
H. viridis , L. 
Leaf: The arc of bundles here is almost closed, being very circular, 
the narrow gap being caused by the ventral groove of the petiole. About 
the middle of the organ occurs, at one end of the arc, in the case of one leaf 
examined, a minute bundle with inverted orientation, which lies in the 
lateral corner of the ventral side, and evidently represents the last vestige 
of the row of inverted bundles which once connected the two ends of the 
arc ; it dies out below ; its upward course I did not trace. The bundle at 
the other end of the arc is incurved, but has not gone the length of 
abstricting off a bundle. A ventral inverted bundle also occurs opposite a 
bundle near the middle of the arc in the base of one of the subdivisions of 
the lamina ; further along the same subdivision it does not occur. About 
half-way down the petiole, in one leaf examined, the two end-bundles of the 
arc are perfectly concentric , with central xylem (Fig. 6); which is due 
Y y 2 
