36 
REPORT ON BOTANY, MDCCCXLI : 
relation of their development to each other ; hence a vegetatio 
peripherico-terminalis takes place. 
VII. On the Structure and Growth of the Chenopodeae 
and Amarantliaeem. — A double system of vascular bundles 
exhibits itself in these stems, an internal one, connected 
together through the entire stem, and situated in the pith 
or at its edges, and an external system, likewise connected 
together through the entire stem, and which increases itself 
from the outside, forming, as it were, the wood. The two 
systems are perfectly different from each other in point of 
essential composition ; but the internal system, which provides 
the appendicular parts with vessels, and the external system, 
which belongs to the stem, are both found in such a way^ 
that (excepting that each vascular bundle enlarges itself to 
a certain extent in its diagonal towards the outside) only 
one uniform progressive growth towards the upper end can 
be perceived. The type of a vegetatio peripherico-terminalis 
is, however, also manifest here, if we regard the fact, that 
the stem, through the agency of the continual formation of 
new layers of wood, grows towards the outside. 
VIII. On the Structure and Growth of the Arborescent 
Dicotyledons. — The author infers, from the examination of 
young willow twigs, that the vascular bundles, which contain 
the vessels of the medullary sheath, correspond with the central 
system of vascular bundles of the herbaceous Dicotyledons, 
only with this difference, that the cardinal vascular bundles 
seem to be wanting in the system of the latter, whilst they 
maintain a distinguished position in the former plants. The 
real woody substance is formed here, as well as in the herba- 
ceous Dicotyledons, by a peculiar system of vascular bundles, 
having nothing to do with medullary sheaths, and forms a 
mass, which, by means of proseiichymatous wood cells, possess 
a tendency to increase from within outwards. For the better 
explanation of the whole, I will add to the preceding, one 
sentence from the author’s general inferences : — In all plants 
provided with vessels, there are only tliree kinds of vegetation ; 
428 
