THE ANATOMY OF THE NODE IN ANGIOSPERMS 317 
CONTORTAE 
All genera examined of the five families included by Engler in the 
Contortae are unilacunar save Menyanthes which (with another genus) 
composes the sub-family Menyanthoideae of the Gentianaceae. In 
this case three or five bundles enter the base of each leaf from as 
many gaps. Either Menyanthes should not be included under the 
Gentianaceae or else we must believe that its nodal structure has been 
so modified by its aquatic habitat, which has caused its leaves to 
become sheathing, that evidence from this region should be disregarded. 
In the Ericales, Ebenales and Contortae the single leaf-trace shows 
no indication of being three-lobed, a fact which may be taken to 
indicate that the unilacunar condition in these orders has been produced 
by the loss of the two lateral traces rather than by the approximation 
of the original three. 
TUBIFLORAE 
This immense order is characterized almost without exception by 
a nodal structure which is unilacunar (figs. 25 and 26). In the many 
genera from the sixteen families of this order investigated only Cyrtan- 
dra, one of the Gesneraceae, displayed other than this single-gapped 
condition. Three or five strands and gaps is typical for this genus. 
Such an exception may be regarded as merely one of the cases where 
the anatomy of the node is not conservative ; or it may be taken as an 
indication that the Gesneraceae are relatively primitive among the 
Tubiflorae and connect such families as the Bignoniaceae and Scro- 
phulariaceae with the Rubiales. 
The leaf-trace in the Tubiflorae is very often three-lobed or tri- 
partite (fig. 25) indicating that it has had its origin as a fusion of the 
three bundles of the ancestral trilacunar type. On evidence from 
nodal anatomy the Tubiflorae as defined by Engler appear to be a 
very natural order. 
Plantaginales 
Plantago is trilacunar. 
Rubiales 
All families in this order save the Adoxaceae were investigated. 
The Caprifoliaceae, Valerianaceae and Dipsacaceae are entirely tri- 
lacunar except for a few instances (Sambucus and others) where they 
may be five bundles and gaps. The Rubiaceae, however, are over- 
whelmingly unilacunar, the only exception observed being the genus 
