22 1 
Herbaceous Type in the A ngio sperms. 
ling in Potentilla , Fragaria , Agrimonia , and other Rosaceous genera. 
Inasmuch as these forms, especially those studied by Dr. Jeffrey, are 
herbaceous, the dissected cylinder seems to be clearly indicated as a recent 
modification. What, then, has given rise to the story of the fusion of the 
bundles into a ring, universal in our textbooks, and so commonly taught ? 
A few forms only have been examined because these seemed to show well 
the desired relations ; and it is true, indeed, that the illustrations chosen, 
viz. Clematis , Aristolochia, and Quercus, seem to vouch for the conventional 
view of the derivation of woody plants from herbs. Often diagrams are 
inserted in textbooks without specification of the plant used. Clematis 
and Aristolochia , which are apparently the usual basis of such diagrams, are 
vines — plants with a structure peculiar to themselves. They can hardly be 
considered types illustrating the growth of the xylem mass in woody 
Angiosperms in general. 
In Quercus , another commonly used type, on the other hand, the 
writer could find no distinct bundle structure, as some diagrams would 
indicate. The protoxylem is not confined, as is usually stated, to a few 
projections of the xylem into the pith, but is distributed in many small 
groups, which appear nearly or quite simultaneously close together along 
the edge of the pith. The latter is strongly angled, and at some points 
along its edge slightly greater primary growth may occur, representing 
leaf-traces in the stem. Mr. Bailey’s paper, which will appear with this, 
explains clearly the structural conditions in this genus which have led 
to its use to illustrate bundle-fusion. It is to be remembered that here we 
have a row of protoxylem groups, small, but close together, encircling 
the pith. External to these groups arises a continuous cambium ring, 
which forms xylem and medullary rays, the latter continuous with the 
pith between the protoxylem groups. Other rays not reaching the pith 
appear, of course, later in the wood. 
In Aristolochia , the plant probably most used to illustrate bundle 
fusion, an examination of the very young stem showed that protoxylem 
groups arise at very nearly or quite the same time at a number of definite 
points (about twelve) where later the bundles form. A cambium ring 
arises outside these as in Quercus , forming first opposite the protoxylem, 
and then extending across the interfascicular tissue. This rapidly forms 
xylem in the bundles, and lengthens radially the wide medullary rays. 
It lays down, however, no new intermediate bundles. Those already 
formed become wider as the stem increases in size, and compress the 
rays somewhat. New large rays appear in the original bundles, dividing 
them externally. In comparison with Quercus we find the chief differ- 
ences to be a restriction of the protoxylem to definite points, and 
the consequent formation of fewer, but very much larger medullary 
rays, that is, rays reaching to the pith. Moreover, this stem is marked 
