1904] CURRENT LITERATURE 315 
conditions (temperature, light, etc.) and the location of the sap stream were 
extensively studied, though not always in the light of physiological knowledge 
ready available. It seems clear from the results that both gas pressure due 
to rising temperature and osmotic pressure in living cells cause sap to flow 
from the tap holes, but it is obvious that the latter agency is much more 
important than has hitherto been believed. The practical problems of the 
Sugar orchard have also been considered, and the results of the experimental 
work regarding them certainly furnish a basis for better practice than has 
obtained hitherto.—C. R. B. 
. A. BONSER has given a detailed account of Big Spring Prairie, Ohio, 
involving the results of several years of careful study.? The place is of much 
interest, since it represents a type of the edaphic prairies of the east. The 
Study was also peculiarly timely in view of the artificial changes which the 
place is now undergoing, The prairie, like most edaphic prairies, represents 
a former lake bed. The author thinks that the general absence of trees is 
due to the dense sod, which precludes germination. That trees and shrubs 
thrive in the prairie is shown in burns and other modified places, where a 
foothold is given. The order of encroachment of trees in such places as well 
as on ridges of sand, clay, and rock, was studied and reported in detail. A 
matter of floristic interest is that this prairie is the most southern known habitat 
of Betula pumila in Ohio.— H. C. CowLes. 
New York Forest, Fish, and Game Commission has recently 
issued a valuable publication on tree planting on streets and highways.” 
Among the subjects discussed are: the selection of trees, street planting, 
Pruning, protection from insects, autumn foliage, municipal control, and the 
legislation of several states in regard to tree planting. The improvement of 
highways i in the country and of property in the city by tree planting is force- 
fully presented. In regard to the latter the author says the planting and care 
of trees belongs to the city government as much as street paving. The work 
contains many excellent illustrations of the beautifying of streets by tree 
planting; also numerous plates showing the natural coloration of autumn 
leaves.— C. D. How 
THE CHIEF interest in a paper by Emile Boulanger on the mycelium of 
the truffle lies in his claim that it is composed of polyhedric cells, and that 
several Hyphomycetes are conidial forms of the truffle!" —H. HassELBRINS, 
*Bonser, T. A., Ecological study of 5 Spring prairie, Wyandot county, Ohio. 
Ohio “eat eo Special paper no. 7. pp. 96. Columbus. 1903. 
* Fox, W. F., Tree planting on streets and highways. Imp. 8vo. pp. 50- pls. 21. 
Albany: J. B, pee Co. 
*Bou GER, E., Les mycelium truffiers blancs; and Germination de l’ascospore 
de la truffe, pp- 20 and 23. f/s. 5. Rennes, Paris: Published by the author. 1903. 
