THE STEM OF RHYNCHOPETALUM MONTANUM. 443 
cortical bundles (a, a). These, as above noted, often split up 
and again coalesce, thus forming a series of loops. Further, the 
successive spirals are connected one with another by branch 
bundles, which run almost vertically (b in the figures) The 
space between them is thus cut up into a number of diamond- 
shaped areas; through the centre of each of these areas the 
central bundle of a leaf-trace passes on its course from the leaf 
(orleaf-scar) to the central ring of common bundles, thus de- 
scribing a course in a direction perpendicular to the surface of 
the cylindrical network of cortical cauline bundles. As each 
bundle passes through the network, it gives off right and left 
branch bundles, which are the branches connecting the lateral 
bundles of the leaf-trace with the central bundle. These, as 
above described, are connected with the cortical system at or 
near to the point where they curve suddenly in their course. 
The result is that in old stems it appears as though lateral 
bundles of the leaf-trace were given off originally from the net- 
Work of cauline bundles, whereas in reality the cauline system 
is of later origin, and connects the earlier-formed vascular 
systems of successive leaves one with another. The position of 
the four-sided leaf-sears and of the several bundles of the leaf- 
trace relatively to the network of cortical bundles will be readily 
understood on comparing figs. 4 & 5, Pl. XXXVIII. 
Besides the bundles hitherto described, other smaller branch 
bundles may be seen in old stems traversing the outer portions 
of the cortex (fig. 2); the course of these does not appear to be 
constant, and has not been accurately followed. 
As it grows older the stem increases in bulk. Judging from 
a single dry specimen of an old stem in the museum at Kew, 
this would appear to be chiefly due to a secondary increase of 
the bundles of the normal vascular ring, which, in the specimen 
in question, is nearly 2 inches in thickness. But the bundles of 
the cortical system, as well as the central bundles of the leaf- 
trace, also increase in bulk, and appear, in the large specimen at 
Kew, at least 4 inch in diameter. 
No system of cortical bundles was found, even in the oldest 
roots examined, 
It remains to draw a comparison between this abnormal arrange- 
ment of bundles in Rhynchopetalum and that in other plants. 
Among Dicotyledons, cortical bundles formed at an early period 
in the growing stem, and having a definite position relatively to 
