1922] CURRENT LITERATURE 413 
of root development of cereals in each seems to be in true prairie 100 per cent, 
in mixed prairie 80-95 per cent, and in short-grass plains 51-79 per cent. 
The experimental data are given in the form of tables, drawings, and photo- 
graphs, all of excellent quality. It is recognized that variations in root develop- 
ment are caused by various factors, such as the chemical and physical character 
of soils and the evaporating power of the air. The soil factors are most effective 
through water content and aeration. The water relations of the various 
habitats were examined by WEAVER by means of atmometers and by soil 
moisture determinations, the latter being interpreted by means of the wilting 
coefficient and hygroscopic coefficient. He calls attention to the recognized 
fact that many plants are able to continue to absorb water below the limits 
of the wilting coefficient. In fact, it is in the responses of different plants 
to the use of soil moisture lying between the limits of the wilting and the 
hygroscopic coefficients that differences appear which might be used with 
advantage for a most significant classification. All wilting, whether clearly 
manifest or not, takes place at about the same moisture content, that is, at 
the wilting coefficient. As the moisture passes below this point the hydro- 
mesophytes soon die, the mesophytes live for a somewhat longer time, while 
xerophytes or drought-resistant plants prolong their existence for a very 
considerable period, reducing the soil moisture to the hygroscopic coefficient. 
It seems rather clear from the work of ALwAy and others, however, that the 
water absorbed below the limits of the wilting coefficient is quite insufficient 
for growth and merely serves to sustain life, indicating that the term “growth 
water” has been correctly used by the reviewer and others for the amount of 
soil moisture i in excess of that indicated by the wilting coefficient. 
ile all of WEAVER’s investigations of root development have been of 
the highest order, this report shows a decided advance, for the accumulation 
of data has become sufficient to permit some significant generalizations. 
Among other things he points out that as our knowledge of root development 
in various associations increases it will render more accurate our interpretation 
of the indicator significance of the natural vegetation. Thus the contribution 
he has made to the science of ecology becomes most useful in the practice of 
agriculture—Gro. D. FULLER. 
Sturtevant’s notes on edible plants 
The purpose of this large volume,3 as indicated in the preface, is that 
new knowledge may be available as follows: (1) the original home of many 
esculents is given for the first time; (2) new landmarks in the histories of edible 
plants are pointed out; (3) an effort is made to mention all cultivated esculents; 
(4) although the book contains much new information as to the history of the 
3 Heprick, U. P. (editor), SruRTEVANT’s notes on edible plants. Report N.Y. 
Agric. Exper. Sta. for 1919. 2:4to. pp. vii+686. Albany: J. B. Lyon Co., State 
printers. 1919. $2.75. 
