1922] WATERMAN—PLANT COMMUNITIES II 
moister conditions of lower layers and the low wilting coefficient of 
sand would prevent a serious deficiency of moisture for plants 
adapted to that habitat. The very dry weather in the first part of 
the summer of 1921, however, apparently caused serious results, al- 
though the full effects of these conditions cannot yet be determined. 
The leaves of the blueberries and other small shrubs dried up early, 
and while the plants were not killed, their vegetative development 
for the following summer was greatly reduced. A number of oak 
and pine seedlings up to two feet in height were evidently killed. 
Fic. 4.—Typical sand ridge vegetation, with Pieris aquilina in center 
Similar “red summers” were reported by the farmers as having 
occurred at intervals of eight or ten years. It is evident that they 
would profoundly affect the development of a dense growth of trees 
on these ridges. Various fires, chiefly prehistoric, have also had 
an influence. The areas which were affected by these fires should 
be determined and mapped, and their influence on the present 
vegetation more definitely determined. 
Morphology and distribution of communities 
MOVING DUNE FORMATION.—The dune vegetation is practically 
the same as that of the Point Betsie dune complex already described 
