4 
of all members of the Guettardeae (indeed, 
of almost all Rubiaceae), the major venation 
of the leaf consists of a midrib with a pinnate 
series of secondary veins arranged in a camp- 
todromous manner (Ettinghausen, 1861: xvi); 
that is, the extremities of the secondaries 
curve acropetally near the leaf margin. In 
addition to the secondaries there are other 
prominent but smaller veins which diverge 
from the midrib and extend toward the mar- 
gins. These intermediate veins (Foster, 1950: 
163) are, however, entirely enclosed within 
the panels or areas delimited by the secondary 
veins. Such areas will henceforth be referred 
to as intersecondary or intercostal panels. In 
actuality the distinction between some inter- 
mediate veins and strong tertiaries is arbitrary 
because the two do intergrade. 
PACIFIC SCIENCE, Vol. XIII, January 1959 
In the mature leaf, tertiary veins and veins 
of lesser categories are not readily distinguish- 
able. Hence it is convenient to refer to the 
entire intercostal venation exclusive of the 
obvious intermediates as the minor venation. 
It is the pattern, histology, and ontogeny of 
the minor venation with which the present 
study is particularly concerned. In a cleared 
leaf (Fig. 1) the minor veins, except for oc- 
casional obvious tertiaries, are fairly uniform 
in size and relative prominence. The ultimate 
areoles (smallest units of mesophyll com- 
pletely enclosed by veins) are delimited for 
the most part by veins of the fifth and sixth 
orders. However, for the above mentioned 
reason, vein categories within the system of 
the minor venation will not be considered in 
descriptions to follow. 
Fig. 1. Portion of a cleared lamina showing the general nature of the mature venation, X 7. Midrib at left; 
several secondary veins in part extend diagonally toward upper right. 
