220 
E antes. — On the Origin of the 
through this region show that the dissection is due to the cutting out of the 
leaf-traces which are set off one, two, or three internodes below their exit ; 
and that the traces of the lowermost leaf are first set off, then those of the 
others in succession. Fig. 4 shows this process at the base of the upright 
stem of G. rivale . That is, the bundles of the herbaceous stem thus formed 
represent leaf-traces and segments of the original cylinder, the common 
bundles of the stem. The short distance within which these traces first 
appear separately and the large number connected with each leaf com- 
plicate the interpretation of conditions here considerably. It is to be noted 
that some of the traces extend as such through two or three internodes. 
The condition here, especially in Potentilla , seems significant. The pros- 
trate biennial or perennial stem has an unbroken central cylinder, a small, 
but thoroughly typical woody stem, and the same condition is found in the 
seedling. The central cylinder of the erect, annual stem, very soon after 
its derivation from the solid cylinder of the rhizome, breaks up to form the 
type of stem characteristic of annual plants. 
Some members of another group of plants, the vines, deserve attention 
at this time, because they have been used as examples to show the sup- 
posed development of the solid woody cylinder by the fusion of originally 
separate and distinct bundles. In such forms as Clematis we find several 
large bundles separated by broad rays, but lacking within the bundles 
themselves all rays, even the uniseriate or primary rays. It is probable 
that this structure is one of adaptation to the habit of the plant. By the 
enlargement of the interfascicular rays sufficient ray parenchyma may have 
been acquired, causing the rest to disappear. In support of this view may 
be cited the case of Vitis. The mature wood of Vitis possesses ordinarily 
only large or secondary rays — for example, the species V. vinifera , L., 
V. labrusca , L., and V. aestivalis, Michx. The seedlings of the first two 
species, however, show distinct uniseriate rays rather abundantly in the 
substance of the bundle. Further, similar uniseriate or primary rays occur 
in the mature wood of V. californica. This appears to be clear evidence 
bearing on the suppression of these small rays. This condition in the 
fibro-vascular segments of Vitis , and probably also of Clematis , moreover, 
is homologous with that demonstrated above in the higher herbs, where the 
bundles have lost all internal rays, and the interfascicular parenchyma 
is very greatly developed. 
We have thus considerable evidence pointing to the derivation of the 
herb from the woody plant. A solid tubular cylinder has been shown by 
Jeffrey, 1 from investigations made upon the Ranunculaceae, Nymphaeaceae, 
and Saxifragaceae, to be the primitive condition of the stele in the Angio- 
sperms. Similar conditions have been disclosed by the study of the seed- 
1 Jeffrey, E. C. : The Morphology of the Central Cylinder in the Angiosperms. Trans. Canad. 
Inst., vol. vi, 1899. 
