in the Evolution of Herbaceous A ngiosperms. 527 
* 3. In the aerial axes of woody herbs a constant and practically never- 
failing distinction from trees is the formation of large foliar storage rays 
about the incoming leaf-traces, as they pass through the woody cylinder. 
4. In woody herbs the foliar storage rays are well developed in the radial 
direction, but their vertical extension is slight. 5. In the aerial stems of 
more slender and less woody dicotyledonous herbs the foliar rays become 
elongated vertically to compensate for their reduced radial dimension 
resulting from the thinning down of the woody cylinder. 6. In rays of the 
type described in 5, the lower part of the radial parenchyma related to the 
foliar trace is often bifurcated by a tongue of unmodified wood. 7. I'he 
vertical elongation of the foliar rays and their subdivision in the manner 
described in 6 result in the final separation of the originally continuous woody 
cylinder into a series of separate strands. 8. The final stage of the herbaceous 
Dicotyledons is a condition in which the cylinder is thinned to such a degree 
that the radial extension of the foliar rays is virtually eliminated. With 
this condition is usually associated a great development in length of the 
portions of the foliar ray flanking the leaf-trace on either side.’ 
As evidence in favour of conclusion No. 3, Jeffrey and Torrey figure, on 
the one hand, stems of trees (Tilia y Ulmus, and Robinia) which are devoid of 
foliar rays and which have continuous vascular cylinders, and on the other 
hand stems of herbs ( Abutilon , Oenothera , Boehmeria, Melilotus , and various 
Compositae) which have foliar storage rays and which possess more or less 
conspicuously dissected steles. That the material selected by them is not 
representative for all trees and herbs, and is, therefore, extremely misleading, 
is shown by a study of the comparative anatomy of the Dicotyledons as 
a whole. Trees with 4 foliar rays ’ occur in family after family of the Dico- 
tyledons from the Casuarinaceae to the Compositae. Not only do many trees 
have the so-called foliar rays, but many of them have the vertically elongated, 
flanking rays which are considered by Jeffrey and Torrey to be charac- 
teristic of an advanced stage of herbaceousness. The arborescent Dillenias, 
for example, have 4 foliar rays ’ which are of the same type as those figured 
by Jeffrey and Torrey 1 for Helianthus annuus and Boehmeria nivea . In 
these woody types, the entering leaf-traces are entirely enclosed in a jacket- 
ing mass of parenchyma : flanking parenchyma, confronting parenchyma, 
and parenchyma of the foliar gap (Figs. 13 and 1,9). The confronting 
parenchyma extends some distance below the node (Fig. 19), and the flank- 
ing sheets of storage tissue are projected far down the stem (Fig. 20). Thus, 
the vascular cylinder is dissected into a series of discrete woody segments 
which are separated by wide rays (Fig. 10). 
It is evident, therefore, that Jeffrey and Torrey’s conclusions, that 4 in 
the aerial axes of woody herbs a constant and practically never-failing dis- 
tinction from trees is the formation of large storage rays about the incoming 
leaf-traces ’ and that 4 the vertical length of the foliar ray, other things being 
1 Bot. Gaz., lxxi, PI. II, Fig. 12; Ann. Bot., xxxv, PI. XII, Figs. 18 and 19; PI. XIII, 
Fig. 32 . 
