THE STEM OF RHYNCHOPETALUM MONTANUM. 441 
the lower part of the stem, are undoubtedly of use in carrying 
on the life of the plant when the main axis, having flowered and 
fruited, dies down, as in the case of Agave (Richard, l.c.). They 
are used in propagating the plant artificially. 
Not only is Rhynchopetalum remarkable among the Lobeliacez 
for its size and external appearance, but also for its internal struc- 
ture. Lobelia macrostachya, L.splendens var. ignea, and L. Erinus, 
also Siphocampylus, have been examined ; but the structure of 
the stem of these plants was in each case found to be normal. 
The early stages of development of the vascular system of the 
stem and leaves were studied in the young axillary buds above 
mentioned. It is assumed that the structure of these is not 
unlike that of young seedlings. The latter have not been inves- 
tigated, since the available plants at Kew had all been derived 
as axillary buds from older plants, and not raised from seed. 
In these young axillary buds the arrangement of the leaves is 
simpler and less crowded than on older axes; and therefore the 
vascular connexions of each leaf can be more accurately distin- 
guished from that of its neighbours than is possible in older stems. 
Successive transverse sections of such buds show that the first 
formed bundles are those which take a median course in the 
young leaf (x in figs.), and on entering the stem pass inwards 
and arrange themselves in the normal manner, in a more or less 
regular circle, about the centre of the axis. Shortly after these 
the first pair of lateral bundles of the leaf-trace are formed (y in 
figs.), which likewise run directly into the stem, perpendicular 
to its surface, then, curving suddenly towards the central bundle, 
they coalesce with it in the cortex at points nearly opposite one 
another, and at a short distance outside the ring of bundles 
above described. This coalescence of the first pair of lateral 
bundles of the leaf-trace with the central bundle seems to be the 
rule, though in the older stems such a connexion is not always 
to be made out, and it is possible that it does not always oceur. 
Almost simultaneously with the first pair, or slightly later, a 
further pair of lateral bundles appears (z in figs.), the connexions 
of which are less regular than those of the first-formed pair; 
they are, however, attached, in the majority of cases, and espe- 
cially in young buds, to the bundles of the first pair. The 
minute structure and compositiou of the young bundles present 
no peculiarities worthy of special remark. 
Thus we have in the young bud of Rhynchopetalum a leaf-trace 
