246 Jeffrey and Torrey . — Transitional Herbaceous Dicotyledons. 
tion just referred to is particularly well seen in Compositaceous stems of 
the proper degree of advance in the herbaceous direction, it also occurs in 
many other groups, where the necessary conditions are realized. It is 
a striking example of the inaccuracy which we have often had to 
note in our critics that they deny the possibility of the topography which 
we have represented photographically in Figs. 20 to 23 for the Ranuncu- 
laceae and the Euphorbiaceae. Hundreds of similar cases could be supplied 
from common herbaceous types. 
Another and more advanced phase of the evolution of the herbaceous 
type is the thinning down, in an even more marked degree, of the axis. 
This automatically results in the elimination of the parenchyma of the foliar 
ray, which radially subtends the foliar trace. As a consequence of this 
condition, only the flanking parenchyma of the foliar ray persists. This 
situation is shown in our Figs. 11 and 12, and also by Text-figs. 3, 4, and 5. 
It has been maintained by our critics that the herbaceous type in the 
Dicotyledons is merely the result of the progressive thinning of the woody 
cylinder. This condition is undoubtedly true for some Vascular Cryptogams 
of herbaceous habit, but cannot be accepted for the Seed-plants. The 
Coniferales, for example, have never given rise to plants either herbaceous or 
vine-like, in spite of the fact that they exist often under climatic conditions 
extremely favourable as regards low temperature to the appearance of the 
herbaceous habit. The reasonable inference from this state of affairs is 
that the Conifers lack some fundamental feature of organization which is 
essential to the development of the herbaceous type among the Seed-plants. 
We are by no means compelled, however, to take refuge in negative evidence 
in this respect, for it has been shown by numerous examples drawn from 
woody or transitional herbs, in the foregoing pages, that a constant and in 
fact diagnostic feature of the herbaceous type in the Dicotyledons is the 
presence of those structures which we have designated foliar rays. As 
explained above, these arise in the first place and in many woody herbs 
from the accentuation of the ordinary rays of the wood in proximity to, and 
especially below, the entering foliar traces. These aggregations of rays, by 
the process of compounding, are transformed later into considerable foliar 
bands of longiradial storage tissue. It follows from the statement of the 
manner of origin of herbs in the Dicotyledons that it is the result of advance 
and differentiation, and is not the consequence of a mere process of 
degeneracy,- as assumed by our critics. Angiosperms are, in fact, as has 
been pointed out by one of us in a recently published text-book of anatomy, 
characterized by the development of dynamic herbs in contrast to the 
Vascular Cryptogams, which are represented in the living Flora by 
degenerate herbs. 
