24 BOTANICAL GAZETTE ~ [JANUARY 
leaf base are 6 others, emphasized in the diagram by the radial 
hatching of their outer regions. It is obvious that the traces of 3 
leaves can be seen simultaneously in transverse sections of the 
stem. In other words, the leaf traces, together with their accom- 
panying leaf rays, by their much elongated downward extension 
constitute an important topographical feature of the stem in 
many herbaceous Dicotyledons. In 6 is shown a corresponding 
diagram for H. orgyalis, a perennial species and one less typically 
herbaceous than H. annuus. Here only the traces of one other 
leaf can be seen. A feature of interest in the development of the 
herbaceous habit in Helianthus is the arrangement of the leaves. 
In the lower regions of intermediate types the leaves are opposite, 
while in the upper nodes the phyllotaxy is alternate. In the woody 
H. hirsutus the phyllotaxy is often opposite throughout. In H. 
annuus and H. argyrophyllus, annual and extremely herbaceous 
species, the leaf arrangement is generally entirely alternate. 
Outstanding features of the organization of the extreme her- 
baceous type illustrated by the Monocotyledons are the occurrence 
of medullary strands and amphivasal fibrovascular bundles. These 
features are likewise present in extreme herbs in the dicotyledonous 
series. Text fig. 4 illustrates these characteristics for the two 
divisions of the Angiosperms. In a is shown the stem of Sanicula 
in the region of the node, where the leaf base is just uniting with 
the axis. An axillary bud is represented by its fibrovascular 
cylinder. The inner bundles of this are uniting by their faces 
with the opposite bundles of the main axis in such a manner as 
to give rise to typical amphivasal strands. These are clearly 
shown in b, which represents a lower plane of section than a. 
the upper side of the cylinder are a number of amphivasal strands 
resulting from fusions between the bundles of axis and branch. 
In ¢ the amphivasal strands have become collateral once more and 
the numerous foliar traces are seen entering the stem. In d 
is shown the nodal region of Rumex sp. The same method of 
formation of amphivasal strands is seen as in Sanicula, namely, 
by fusions between opposed strands of axis and branch. In this 
case the concentric bundles are so numerous as to be brought into 
the medullary region. In e is represented a lower plane of section 
