12 
PACIFIC SCIENCE, VoL XIII, January 1959 
Figs. 19, 20. Paradermal sections of the same area of a lamina at two levels after the ultimate areoles have been 
delimited, X 500. Figure 19 {left) represents a section 12 below that in Figure 20, showing a group of areoles 
enclosed by well-developed procambial strands. The panels of ground tissue will become mesophyll. Figure 20 
{right)-. Same area 12 higher showing pattern of superimposed sclerenchyma, much more intricate, still actively 
differentiating apparently. 
mature lamina which is not basically different 
from that of Liriodendron. In the intervening 
areas of the plate meristem concerned there is, 
then, a decided tendency for groups of elon- 
gate cells to be produced by series of similarly 
oriented cell divisions. From these groups are 
finally differentiated parallel-oriented minor 
veins delimiting areoles which are markedly 
elongate with a tendency to be rectangular 
rather than polygonal. In this respect, Bobea 
to some extent resembles Qtmna, in which 
the entire intercostal venation is derived from 
a plate of embryonic cells in which the gen- 
eral orientation of elongate cells clearly fore- 
shadows the mature, highly lineolate vena- 
tion. It is therefore concluded that the 
ontogenetic sequence in the development of 
the lamina of Bohea represents a divergence in 
its later aspects toward that of QuHna which 
correlates with its difference in foliar vena- 
tion pattern. 
A critical evaluation of the above hypoth- 
esis must await the results from additional 
ontogenetic studies. Further investigations in 
the tribe Guettardeae would be highly re- 
warding, since in this apparently natural 
group there is such a wide variety of venation 
patterns. It is hoped that appropriate material 
of members of this group can be obtained to 
augment the present investigation. Similar 
studies should also be made of other repre- 
sentatives of the Liriodendron type of venation 
to test whether the postulated correlation 
here presented does indeed exist. In addition 
to intensive investigation of selected venation 
types there is also the need for more extensive 
surveys, such as have been initiated by the 
author in the Rubiaceae, to further our under- 
