THE ANATOMY OF THE NODE IN ANGIOSPERMS 309 
The vascular supply to the large leaves of Catalpa comes off from a 
single gap, whereas that to the much reduced ones of certain of the 
Polygonaceae is made up of a considerable number of separately in- 
serted strands. The sheathing leaves of the Polygonaceae and Um- 
belliferae are supplied by a large number of bundles, but in many 
instances in the Caryophyllaceae and other groups the leaves also 
encircle the stem with their bases but into each passes only a single 
strand from the stem. To be sure, there are a considerable number of 
instances where the leaf has been so much reduced from adaptation to 
xerophytic or hydrophytic conditions that it is supplied by a single 
bundle instead of by the three or more which may distinguish the rest 
of its family. In such cases, which of course are comparatively rare, 
the anatomy of the node is of little value in classification. The type 
for a family should be obtained from vigorous, unreduced species. 
Let us now briefly compare the anatomy of the node in the various 
main groups of dicotyledons and endeavor to find what information a 
study of this region presents which will be of value in determining 
relationships. 
Verticillataei 
Each of the much reduced, scale-like leaves of Casuarina is supplied 
with a single small trace. 
PiPERALES 
Among the Piperaceae the genus Peperomia has a normal vascular 
structure and a trilacunar trace. In Piper, where the stem anatomy 
is usually anomalous, the foliar supply consists generally of five or 
seven separate strands. Peperomia thus presumably represents the 
primitive condition for the family. 
Salicales 
In all species of Salix and Populus examined, the nodal structure 
was invariably trilacunar. 
Garryales 
The node of Garrya is trilacunar. 
Myricales 
The node in this group is doubtless primitively trilacunar, but the 
two lateral bundles are small and often absent. 
^ The nomenclature and classification is that of the last (7th) edition of Engler's 
" Syllabus der Pflanzenf amilien. " 
