26 BOTANICAL GAZETTE [JANUARY 
unions of bundles are taking place, with the initiation of some 
amphivasal strands. In / the fibrovascular union of leaf and 
axis has advanced still farther, and many amphivasal bundles are 
present in the stem as a consequence. 
It seems clear from these examples that the entry of numerous 
foliar strands at the node is correlated with the formation of amphi- 
vasal medullary strands. In most Dicotyledons these strands are 
the result of the facial fusion of the bundles of axis and branch, but 
such fusions are usually associated with a large number of foliar 
traces simultaneously entering the stem at the node. In the 
Monocotyledons the amphivasal strands result from the fusion of 
stem bundles with one another, or from the fusion of foliar traces 
with those of the stem in the region of the node. The amphivasal 
strand so characteristic of many higher Dicotyledons and the lower 
Monocotyledons probably originated in the first instance as a 
consequence of the fusions of stem bundles with stem bundles, and 
later, with the still further multiplied number of foliar traces 
characteristic of the Monocotyledons, by fusions of leaf bundles with 
stem bundles. 
_, Conclusions 
The various data introduced in this paper appear to justify the 
drawing of certain general conclusions. First of all, statements 
made as to the absence of foliar rays in herbs are not consistent 
with the facts of anatomy. Such rays are so characteristic a feature 
of organization of the more woody region of. the aerial axis of herbs 
that they constitute a well marked diagnostic feature of such forms. 
The foliar rays of herbs are the result of the aggregation and fusion 
of the ordinary rays of woody stems, in relation to the foliar traces. 
Accompanying and characteristic of the process of fusion is the 
transformation of the vessels into fibers and the septation of the 
latter in turn into parenchymatous elements. The final con- 
sequence of this activity is the formation of large masses of storage 
tissue in relation to the incoming foliar traces. By comparison of 
nearly related species of the same genus, which are progressively 
more herbaceous, the following interesting conditions can often’ 
observed. The accentuation of the herbaceous habit is accom- 
panied by marked increase in the size of the leaf trace and of the 
