448 
EDMUND W. SINNOTT AND IRVING W. BAILEY 
whole leaf began to be developed opposite each departing trace (as 
in the lower vascular plants) but that only the middle one persisted. 
There certainly appears to be some sort of morphogenetic connection 
between lateral leaf-trace and stipule. 
In the case of sheathing leaf bases and the polygonaceous ochrea 
we really have a row of adjacent stipules (each opposite one of the 
numerous leaf-trace bundles) which have become fused together. 
Sometimes, especially in the case of five-bundle nodes, there are two 
broad-based stipules, as in most of the Vitaceae, each opposite a 
♦pair of traces. When the bundles and gaps are more numerous and 
occur round rnost of the stem periphery, as in the Umbelliferae and 
many others, the sheath is much broader and its resemblance to two 
stipules is usually gone; but even in such cases it occasionally 
manifests itself, as in certain of the Magnoliaceae. 
The relation between the stipules of dicotyledons, on the one hand, 
and the ligule of grasses, the tendril of Smilax and the "stipules" of 
the Potamogetonaceae, on the other, has been much discussed. A 
study of the nodal anatomy of these monocotyledonous plants and 
its relation to the appendages in questioil is helpful in determining 
their real nature. 
In the more vigorous species of the Potamogetonaceae, a family 
which modern classifications regard as among the most primitive of 
monocotyledons, three main bundles enter the base of the leaf just 
as in the trilacunar dicotyledons, a much simpler condition than that 
prevailing in most monocotyledons. From the two lateral ones 
branches are sent off into the stipules {fig. 7), so that these organs 
receive their vascular supply in precisely the same way as do the di- 
cotyledonous stipules. On the basis of this evidence the two structures 
certainly appear to be homologous. It is significant that both in their 
nodal anatomy and in the character of their stipular appendages the 
Potamogetonaceae approach the dicotyledons more closely than do 
any other monocotyledons. 
The two tendrils of Smilax, which are inserted at the base of the 
petiole, are apparently homologous with the stipules of the Potamoge- 
tonaceae, for their vascular supply is largely derived from the lateral 
members of a trio of large bundles which, with a number of smaller 
ones, enter the base of the leaf from the axis. 
The ligule of grasses, the vascular supply of which was investigated 
carefully by Colomb, is more complicated anatomically but seems to 
