446 Worsdell . — Origin and Meaning of Medullary 
A smaller specimen examined showed no medullary bundles in the 
internodes, unless the two or three small insignificant strands of scleren- 
chyma opposite a few of the ring-bundles represent their vestiges. In the 
nodes, at each corner of the bay formed by the outgoing vascular ring of 
a branch, a bundle enters the pith and becomes amphivasal, only tore-enter 
the ring at a higher level just before the branch leaves the stem. 
Leaf. 
The scattered disposition of the bundles is very obvious in the petiole. 
In one specimen are two distinct series, of which' the innermost consists of 
very small bundles, evidently vestigial and of no particular or useful 
function. In another specimen there are one or two minute, normally- 
orientated bundles opposite to, and within, the larger ones ; one of the 
larger inner bundles is almost amphivasal, 
while other smaller ones have oblique 
orientation. In another specimen there 
are three distinct series of bundles, of 
which the innermost consists of numbers 
of very small, normally - orientated 
bundles, some of which end blindly 
below in the region where the bundles 
fuse up to form the simple arc which 
eventually passes into the stem ; some 
also are seen to end blindly if traced 
upwards (Fig. 25). 
Some of the outermost (dorsal) 
bundles have on their ventral side, and 
also at their inner corners, one, two, or 
three very small, inversely-orientated 
bundles, which, in the base of the 
petiole, fuse laterally with the large 
bundle (Fig. 25). One or two of these outer bundles are quite concentric, 
with central xylem, due to the fact that the small bundles, which in those 
just described are detached from the sides and become distinct strands on 
the ventral side, are in these cases never detached, but remain a constituent 
part of the whole bundle. 
Dahlia excelsa, Bth. 
Peduncle. 
Herbarium material only was investigated. 
There is a wide lacuna. In the pith, at wide distances apart, are 
a few more or less rudimentary concentric strands consisting, in some cases, 
of phloem only with cambial cells all round it ; in other cases, in addition, 
Fig. 25. Echinacea (. Rudbeckia ) pur- 
purea. Petiole, showing medullary bundles 
{mb). The most peripheral of these 
{pmb) are recent lateral derivatives from 
the arc-bundles to which they are opposed, 
x 4- 
