in the Evolution of Herbaceous Angio sperms. 531 
present which in the first annual ring break up the woody cylinder into 
separate strands. The development of a typical many-bundled herbaceous 
stem from such a condition as this is merely a matter of a progressive thin- 
ning of the vascular cylinder. In a similar manner, herbaceous stems with 
unbroken cylinders, D, may be derived directly from A by a general 
reduction in cambial activity. The explanation proposed by us — aside from 
its greater directness and the fact that it does not necessitate the develop- 
ment of a new structure which is ultimately lost again before the evolutionary 
series has reached its final stages — possesses the advantage of not being 
invalidated by the occurrence of ‘ foliar storage rays 5 in many arborescent 
Dicotyledons, or by their absence in certain groups of herbs. 
Summary. 
1. Recent criticism of our work on the comparative anatomy of woody 
and of herbaceous Dicotyledons is based upon an inaccurate statement of 
our views and has therefore confused the issues involved. 
2 . Our critics attack the conclusions that a progressive thinning of the 
woody ring is the chief anatomical concomitant of the change from a woody 
to an herbaceous habit, and that the woody ring of many-bundled herbs is 
dissected by high, multiseriate rays which are not subtended by woody 
elements on their centrad sides. 
3 . They assert that a new structural feature, the ‘ foliar storage ray 
has made its appearance in the evolution of herbs, and that herbaceous 
stems, therefore, cannot be regarded as essentially similar in construction to 
the young stems of their woody ancestors. 
4. Evidence is here presented that (1) the ‘foliar storage rays’ of our 
critics include several morphologically distinct structures ; (2) many trees 
and shrubs among Dicotyledons do possess ‘ foliar rays and therefore display, 
in their first annual rings, dissected steles precisely comparable to those 
occurring in herbaceous types ; and (3) many herbaceous stems, on the 
contrary, have essentially continuous vascular cylinders and thus do not 
possess ‘ foliar storage rays \ 
5. The hypothesis of our critics that trees and shrubs gave rise to 
c woody ’ or transitional herbs through the development of well-marked 
‘ foliar storage rays ’, and that woody herbs gave rise, in turn, to the still 
more herbaceous types by a loss of the confronting portion of the ‘ foliar 
ray ’ and a downward extension of its flanking portions, is open to criticism, 
since it does not explain the origin of herbs with continuous cylinders, and 
since it involves the evolution and the subsequent loss of a transitional 
structure, when the facts can more easily and simply be explained without 
such an assumption. Indeed, in their discussion of the more herbaceous 
types, the correctness of our major contention is essentially admitted by 
our critics. 
