NOTES AND COMMENT 



Among the topographic features peculiar to the glaciated portions of 

 the United States are small depressions, known as plunge basins, 

 caused by the forceful erosion of waterfalls. Dr. Loren C. Petry has 

 recently described the vegetation of one of these basins in central New 

 York, showing that its plants are all of northern range and many of 

 them absent from the surrounding region (Bull. Torr. Bot. Club, May, 

 1918). He has further described an intensive investigation of the tem- 

 perature conditions of this basin, 600 by 450 feet in size and 95 feet in 

 depth. Oh a warm summer day the temperature at the rim was 

 94° F. and in the bottom 63.5° F., while the humidities in these places 

 were respectively 32% and 73%. The soil moisture, wind and humidity 

 were found to vary little throughout the bottom of the basin, but the 

 observed differences of air and soil temperature were great enough to 

 justify the establishment of twenty stations for the measurement of 

 these conditions. The isotherms of soil temperature were found to 

 correspond with the zonation of the vegetation, the isotherm of 56° F. 

 agreeing exactly with the very similar distributional areas of the five 

 characteristic species of the floor of the basin. The isotherms of air 

 temperature did not coincide with the distributional limits. It is 

 rarely that the causes underlying the distribution of plant communi- 

 ties are so thoroughly investigated and the role of a particular condition 

 so conclusively shown. 



Professor William Trelease, of the University of Illinois, has pub- 

 lished a booklet of 394 pages entitled Winter Botany (privately pub- 

 lished, $2.50), which is a companion volume to his Plant Materials of 

 Decorative Gardening. Keys and descriptions are given which make 

 it possible to determine the native and introduced woody plants of the 

 eastern and central United States in the leafless winter condition. The 

 ingenious keys, full descriptions and excellent illustrations should make 

 the book a very useful one for botanists and horticulturists. Many 

 sub-tropical, European and oriental shrubs are included, as well as 

 some that are native to the western states, and it is unfortunate — even 

 from the gardener's standpoint — that the geographical origin of the 

 trees and shrubs is seldom stated. 



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