BOOKS AND CURRENT LITERATURE 



Field Study of Osmotic Concentration. — Whenever a step is 

 taken which makes it possible to secure data on any aspect of the 

 physiological behavior or condition of plants under field conditions, 

 an important contribution is thereby made to the advancement of 

 plant ecology in one of its most important and fruitful directions. The 

 technique which has been worked out by Harris for securing the sap 

 of plants and determining its freezing point has been simplified and 

 perfected in such a manner that he has been enabled to secure a very 

 considerable quantity of data on the osmotic concentration of plant 

 saps. Following a preliminary paper in Science^ Harris, Lawrence, and 

 Gortner have published the results of their determinations of concen- 

 trations for plants growing in the vicinity of Tucson, Arizona.^ From 

 one to four sets of determinations were made for each of some 124 

 plants, and figures are published for the depressions of freezing point 

 and for the osmotic concentrations in atmospheres. The work was 

 done in March and April, when vegetative activity is high and the 

 moisture content of the soil is neither at its highest nor its lowest values 

 for the year. Plants of every vegetative type were used, and sets of 

 determinations were secured in five localities which differ in the physi- 

 cal and moisture conditions of the soil. Sap was secured only from the 

 leaves, and usually from plants in flowering condition. The lowest 

 values were secured in the annuals, Calypiridium exhibiting 8.3 at- 

 mospheres, Calycoseris 9.1, Parietaria 9.5, and Galium 9.6; and in the 

 climbing root-perennial Cissus, which exhibited a value of 8.6 atmos- 

 pheres. High values were secured for the leguminous tree Olneya, 

 29.7, for Covillea, 34.2, for Yucca, 37.4, for the buxaceous shrub Sim- 

 mondsia, 40.6, for Atriplex growing in a salt spot, 52.0, and for the 

 evergreen celastraceous shrub Mortonia, 57.2. A comparison of the 

 various vegetative types of plants shows that the trees and shrubs 



^Harris, J. A., Lawrence, J. V., and Gortner, R. A. On the osmotic pres- 

 sure of the juices of desert plants. Science, 41: 656-658, 1915. 



2 Harris, J. A., Lawrence, J. V., and Gortner, R. A. The cryoacopic con- 

 stants of expressed vegetable saps, as related to local exivironmental conditions 

 in the Arizona deserts. Physiol. Res., 2, No. 1, pp. 1-50, 1916. 



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