392 BOTANICAL GAZETTE [May 
brackish water, partly on low-lying soil which is rarely, sometimes never, covered 
by salt or brackish water. 
While visiting the islands in 1906, he noted that the extensive mangrove forest 
occupying one of the larger lagoons had perished. The explanation seems to be 
that in 1899 the island was ravaged by a serious hurricane, which so violently 
agitated the sea that large quantities of clay and gravel were washed into the 
lagoon and deposited as a layer several inches thick. This caused so sudden a 
change in the soil constitution as to destroy the forest, although there were clear 
indications that the same formation would eventually reclaim much of the area 
formerly occupied. 
e small trees growing in drier situations seem sufficiently distinct from the 
mangroves to be regarded as a distinct society, which is named the ‘‘ Conocarpus 
formation,” after the most conspicuous member. This formation is regarded as 
very nearly the ecological equivalent of the Nipa formation of SCHIMPER in the 
Indo-Malayan strand flora. The vegetation of the sand strand exposed to the 
wind includes the well-known Pes-caprae formation, an aggregation of shrubs 
designated the Tournefortia formation, and the forest Coccoloba-Manchineel 
formation. The anatomy of several of the strand plants has been investigated, 
and some further studies made of the more xerophytic vegetation of the rocky 
coasts.—GE0, D. FULLER. 
Loess and plant societies.—The intimate relation between physiographic 
plant ecology and geology receives emphasis in the evidence deduced by SHIMEK*® 
to prove that the irregular distribution of loess deposits has been effected by the 
character of formerly existing plant societies. Vegetation is known to play an 
important part in pulverizing the soil, affording anchorage for fine wind-blown 
particles, and finally in returning its own substance to the soil in a finely subdivided 
condition. Thus well-drained areas supporting heavy mesophytic vegetation 
accumulated fine material now appearing as moderate deposits of loess of uniform 
quality. Xerophytic societies of unequal density resulted in inequality and 
irregularity of the deposits, while hydrophytic areas, as well as those of such eleva- 
tion or aridity as to be without vegetation, collected no loess. The very diverse 
aspect of the plant societies on the east and west sides of large streams like the 
Mississippi is found to correspond exactly with the difference in quality and dis- 
tribution of their loess deposits. The interstratification of sand the author 
believes to have resulted from periods of very scanty vegetation caused by climatic 
changes. ; 
While the thesis is essentially an argument in support of the eolian hypothesis 
for the formation of loess, it has many points of interest for the ecologist; for should 
further evidence prove the soundness of the author’s views, it would afford a 
useful key to the distribution of plant societies during recent geologic times. The 
author finds the present edaphic influence of loess evident in the vegetation, even 
3° SHIMEK, B., The genesis of loess a problem in plant ecology. Proc. lowa 
Acad. Sci. 1557-74. pls. 3-7. 1909. 
