Herbaceous Type in the Angiosperms. 217 
confined chiefly to the Rosaceae, with the examination of several vines, some 
members of the Ranunculaceae, and a few plants from other families. 
A general ability to transform xylem into parenchyma exists in a 
number of families among the Dicotyledons. It has been shown 1 that the 
formation of the large rays in Quercns is due largely to such a change. 
Further, Mr. I. W. Bailey, in a paper contemporaneous with this, shows 
that the leaf-trace gives the impetus, by the influence of which woody 
plants form these additional masses of amyliferous parenchyma, and acquire 
thus the advantage of greatly increased storage capacity. This influence 
extends always for a considerable distance below, and also to a less extent 
above, the exit of the trace. The initial stage of parenchymatization is often 
the cutting out from the xylem cylinder opposite the trace of a segment 
which may ultimately be transformed more or less completely into paren- 
chyma. In the woody Rosaceae similar conditions exist ; whereas, in 
herbaceous representatives of the family, parenchymatization occurs in the 
same regions and in much the same way, but is carried much further. 
Some of the woody members show conditions similar to those described 
by Bailey in the Cupuliferae. Species of Rubus , especially of the sub- 
genera Idaeobatus and Cylactis , possess more abundant rays with some 
compounding in the regions below the leaf- traces, and Rubus spectabilis 
shows compounding well developed. Potentilla palustris, in its prostrate 
or procumbent stem, presents very suggestive conditions. In the segment 
of the xylem directly below the exit of each leaf-trace there is a decided 
lack of vessels and an agglomeration of rays (Fig. 1). Moreover, at these 
regions the annual ring dips inward strongly, as is always the case in the 
formation of radial parenchyma in mass in connexion with compounding 
and compounded rays. Further, this leaf-trace influence, so strikingly 
manifested in the corresponding inward dip of the annual ring, extends 
always down through one * and often through several of the internodes . 
Above the leaf-gap there is disturbance for only a very short distance. 
Conditions in the upright stem of this species will be discussed below. 
In the species described above we are dealing with forms in which the 
woody cylinder is as yet fairly strong. Some of the herbaceous perennials 
of the Rosaceae hold perhaps the greatest interest in connexion with this 
problem— for example, certain species of Potentilla , the genera Geum y 
Agrimonia , Sanguisorba , and others. Among these plants we find two 
kinds of stems : a stout, subterranean, or creeping perennial stem, with 
large storage capacity ; and more slender, erect, aerial, annual stems, arising 
from the perennial portion usually as lateral branches. The perennial stem 
is, in most cases, of the woody type, with certain modifications due to 
adaptations as a storage organ, whereas the erect annual stem is more or 
less completely pf herbaceous texture. These two kinds of stems are of very 
1 Eames, A. J. : On; the Origin of the Broad Ray in Quercus. Bot. Gazette, vol. xlix, 1910. 
