436 BOTANICAL GAZETTE [JUNE 
the greatest concentration of soil solution found in beach sands 
in the course of these investigations—at Long Beach, on the 
coast of California—does not exceed the maximum occurring in 
ordinary cultivated soils, according to the above figures. On 
the Atlantic strand the salt content of the sand is generally far 
below the minimum present in ordinary cultivated soils, if not 
actually too small to supply the optimum amount of mineral 
nutrients required by most cultivated plants. 
So far-as the data yet available may warrant a generalization, 
we must theretore conclude that plants of sandy sea beaches and 
dunes are not generally halophytic, although, as is the case at 
Long Beach, species that are elsewhere characteristic of strongly 
saline soils and belong to truly halophytic associations may enter 
into the vegetation of the sand strand. 
We must look to factors of the physical environment other 
than an excessive concentration of the soil solution for an expla- 
nation of the usually distinctly xerophytic character of sand- 
strand vegetation. Among such factors may be mentioned strong 
winds (often carrying salt spray from the surf), intense light 
and a great amount of heat radiated from the surface of the sand 
in summer, all of which would doubtless have a share in bring- 
ing about excessive transpiration from plant surfaces not pro- 
tected by special adaptations. To these factors then we must 
attribute the occurrence in plants of the sand strand (although 
growing in a soil usually amply supplied with water and in an 
atmosphere often nearly saturated with moisture) of many of 
those modifications of structure by which desert plants protect . 
themselves against excessive loss of water by transpiration. All 
these conditions of the environment are common as well to the 
sandy beaches of great freshwater lakes, so that it is in no way 
remarkable, from an ecological point of view, that such typical 
sea coast. plants, for example, as Ammophila arenaria, Cakile 
americana, Lathyrus maritimus, and Euphorbia polygonifolia are 
likewise found on the shores of Lake Michigan. 
U. S. DEPARTMENT OF AGRICULTURE, 
Washington, D. C. 
