STEM, LEAVES, AND BUDS. 
35 
The two systems unite themselves in the node into a fibrous 
net-work, from which spring buds and roots, in such a manner 
that their separated systems of vascular bundles enter into 
immediate connection with those of the stem. The formation 
of the wood only takes place through the peripheral vascular 
bundles, by the production of woody matter on their outside, 
and which consists partly of new vascular bundles, and partly 
of cells of prosenchyma. The system of vascular bundles of 
the appendices is only connected with the central system of 
vascular bundles towards the exterior, and appears as its 
immediate continuation. A part of the same system of vascular 
bundles continues its course upwards, from which it follows, 
that a continued growth of its bundles is peculiar to this 
system of vessels (vegetatio terminalis). The same also holds 
good with regard to the peripheral system of vascular bundles ; 
but since this enlarges itself towards the exterior by the 
deposit of vascular bundles, of a second, third, and fourth 
rate order, it exhibits a complicated vegetation. The author 
calls this mode of growth vegetatio peripherico-terminalis.” 
He then speaks of the structure of the related genera, Sau- 
rurus^ Houttuyniu, and the CJilorantJiece, 
VI. On the Structure and Development of the Nyctagineoe. 
— The following are the results of the researches which the 
author instituted with regard to the formation of the stem 
of the Mirahilis. A double system of vascular bundles may 
be distinguished, an internal and an external one. The inter- 
nal system is simple, and consists of a zone of vessels, and of 
the central vascular bundles enclosed by it, and which enter 
into the leaves ; the external system, on the other hand, con- 
sists of many circles of vascular bundles, which are situated 
one above another, which, independent one of another, are 
formed from the former, and are only cemented by anasto- 
mosis. A peripheral groAvth, in the manner of the Monoco- 
tyledons, does not take place internally nor externally, but 
a growth, progressing towards the axis, that is, a vegetatio 
terminalis. A peripheral vegetation, however, appears here, 
when both systems of vascular bundles are regarded in the 
427 
