118 BOTANICAL GAZETTE [SEPTEMBER 
NOTES FOR STUDENTS 
Veevudien of British Guiana.—Hircucock; has given an_ interesting 
sketch of the conditions of plant life in British Guiana, with notes on the 
flora. The climate shows great uniformity of temperature, the mean maximum 
having the narrow variation of 83° to 87° F., and the mean minimum from 
74.5° to 76.5°F. The annual rainfall ranges from 150 inches in the north to 
50 inches in the south, with a relatively dry period extending from August to 
November. Virgin forest covers the greater part of the country, showing 
many of the characteristics of tropical rain forest, such as stratification, abun- 
dance of lianas, buttressed trunks for the larger trees, and great luxuriance. 
Attention is directed to cleanness of the forest floor due to the destruction of 
fallen trees and branches by decay and by wood ants. This condition is also 
accentuated by the scanty growth of low vegetation due to the density and 
uniformity of the shade. Species of the forest trees are not gregarious, but 
are scattered here and there. 
he flora shows some interesting comparisons with that of the United 
species, as Fagaceae, Cruciferae, Ranunculaceae, Rosaceae, Labiatae, 
Umbelliferae, and Compositae. Some familiar families are found in Guiana 
chiefly as trees, as Euphorbiaceae and Solanaceae. On the other hand, certain 
families sparsely represented in the United States are found in greatly increased 
mbers. otable among these are the Araceae, Palmaceae, Piperaceae, 
Rubiaceae, Myrtaceae, Lauraceae, Sapotaceae, and Melastomaceae. Orchids 
reach their highest development on the mountains.—Gro. D. FULLER. 
Soil moisture.—As a result of recent investigations, PARKER‘ presents 
evidence that the vapor pressure of different moisture contents, the equilibrium 
relations with seeds, and the freezing point depression due to solid material 
do not indicate different forms of soil water such as given by the dilatometer 
method. This would indicate that the old method of classifying soil moisture 
as hygroscopic, capillary, and gravitational, although open to certain objections, 
still remains the best available. The opposing view, presented by Bouyoucos, 
has already been noted in this journal.’ ParkER’s experiments, however, 
tend to support the views of such modern othe as RussELL and KEEN 
that all the water present in the soil is subjected to the same law over the whole 
experimental range, and the various constant and critical points shown by 
soils at varying degrees of water content are equilibrium values only, and 
do not indicate any break or abrupt change in the physical condition of the 
soil moisture. 
3 Hircucock, A. S., Floral aspects of British Guiana. Ann. Rept. Smithsonian 
— pa cathe Lg 293-305. pls. 12. 1921. 
F. W., The classification of soil moisture. Soil Science 13:43-54- 1922- 
5 Ah Bi 733420. 1922. 
