Foliar Venation — Pray 
5 
The ultimate areoles of Bobea display a 
marked tendency to be rectangular and often 
distinctly elongated. While actual areole 
shape is extremely variable the tendency to- 
ward rectangularity is well enough expressed 
to give the minor venation a distinctive char- 
acter which is readily distinguishable from the 
minor venation of such a leaf as that of Liri- 
odendron and many other dicotyledons with 
their polygonal areoles. The tendency of the 
minor venation to be made up of elongated 
areoles is interpreted as a weak expression of 
the lineolate type of venation which becomes 
highly developed in some members of the 
tribe Guettardeae (Pray, 1953: 174-233). 
While the cleared leaf at low magnifications 
(as in Fig. 1) displays quite obviously the 
general character of the minor venation, the 
abundant sclerenchyma in the blade does ob- 
scure the details, particularly as regards the 
occurrence and nature of vein endings. There 
are fibers associated with every vein. In trans- 
verse section (Fig. 6) the fibers, which are 
located adaxial to the tracheary elements, are 
shown to comprise in fact the greater part of 
the vascular bundles. Strands of fibers and 
individual fiber cells extend from the vascular 
bundles into the mesophyll, in the region 
within the palisade layer, and between the 
palisade and hypodermal layers (Figs. 2, 3, 6). 
Careful study of cleared leaves at higher mag- 
nifications (Figs. 2, 3) shows that structures 
appearing to be vein endings are actually de- 
void of conductive tissues as such and consist 
of sclerenchyma only. Thus drawings of the 
true conductive system (Figs. 4, 5) show that 
most of the areoles lack vein endings. The 
latter are rather rare, in fact, in the present 
material. Apparently areoles without freely 
terminating vein endings are infrequent in the 
foliar venation patterns of dicotyledons in 
general (Esau, 1953: 424). 
Figs. 2 {left), 3. Small areas of the cleared lamina showing the nature of the ultimate areoles, X 65. Note 
fibers extending from the veins into the mesophyll. Arrow in Figure 2 indicates an idioblastic sclerenchymatous 
element. 
