336 



SCIENCE 



[N. S. Vol. LIII. No. 1371 



easily examined. Until very recently no at- 

 tempts have been made to extend observation 

 and description to the subterranean parts of 

 land plants, but excellent beginnings in this 

 recondite province of botany are now avail- 

 able and enough has been accomplished to 

 demonstrate that a well-rounded knowledge 

 of plants or of any plant individual must in- 

 clude just as thorough study of root systems 

 as has been devoted to the aerial parts. 



Publication No. 292 of the Carnegie Insti- 

 tution of Washington is perhaps the most 

 valuable contribution yet available in this new 

 field. In this book Weaver presents the re- 

 sults of an enormous amount of detailed study 

 devoted to the form and distribution of the 

 roots of plants growing in the grasslands of 

 the United States, this study being a continua- 

 tion of the author's earlier volume on " The 

 Ecological Eelations of Eoots." " Practically 

 all of the grassland dominants have now been 

 studied, many of them in two or more asso- 

 ciations and under widely different conditions 

 of environment." Descriptions of 38 new root 

 systems of native plants are here presented and 

 " more than 80 examinations of the root sys- 

 tems of crop plants have been made in widely 

 varying soil types and conditions of growth." 

 The root systems have been excavated with 

 painstaking care and their form and distribu- 

 tion are set forth by descriptions and by dia- 

 grams drawn to scale, being frequently also 

 illustrated by reproductions of photographs. 



The point of view is primarily that of what 

 may be called the Nebraska school of ecology, 

 with much emphasis on the concept of plant 

 succession and on the practical value of a 

 knowledge of native vegetation as an indicator 

 of agricultural possibilities. 



The phenomena of plant succession, whether 

 ecesis, competition, or reaction, are controlled so 

 largely by edaphic conditions and particularly by 

 water-eontent [of the soil] that they can be prop- 

 erly interpreted and their true significance under- 

 stood only from a thorough knowledge of root re- 

 lations. 



But the discussions involve much of the. 

 physiological, and the author's aim appears 



generally to be a consideration of the indi- 

 vidual plant as a machine operating under 

 the controlling conditions of the surround- 

 ings, both above and below the soil surface. 



Since the work of charting root systems is 

 very arduous and since the physiological proc- 

 esses of agricultural plants deserve attention 

 before native plants are to be thoroughly 

 studied in this way, it is especially gratifying 

 that a goodly number of crop plants have 

 received attention at the author's hands. 

 Some sti'iking points are shown by the follow- 

 ing illustrations (from p. 139) : Sweet clover 

 {Melilotus) 116 days old had tops 1.8 ft. high 

 and roots about 5 ft. deep in lowland soil, 

 while the tops were only 1.5 ft. high and the 

 roots were mainly about 5.8 ft. deep in upland 

 soil. Oats {Avena) 75 days old had tope 3 ft. 

 high in lowland and 2 ft. high in upland soil, 

 the corresponding " working depths " of the 

 roots being 2.6 and 3.1 ft., respectively. 



The presentation of the results of these 

 valuable investigations might rather easily 

 have been rendered more generally clear and 

 more readily comparable with the results of 

 other similar studies, if the author had em- 

 ployed a meter-stick instead of his foot-rule. 

 He does not appear to be consistently opposed 

 to the use of the metric system, for some 

 measurements are recorded in millimeters, 

 etc., and he has grafted the decimal char- 

 acteristic of the better system on to the unit 

 of the worse; he dealt primarily with feet and 

 inches but reduced his final values to terms 

 of the foot and its decimal fractions. 



The root characteristics of a given species 

 are found to be " often as marked and dis- 

 tinctive as are those of the aerial vegetative 

 parts," in spite of profound differences fre- 

 quently concomitant with marked differences 

 in habitat conditions. Different species of the 

 same genus are sometimes markedly different 

 in their root characteristics. 



The volume should be familiar to all who 

 are interested in the relations that obtain 

 between plants, on the one hand, and the soil 

 and air conditions of their surroundings, on 

 the other. 



B. E. Livingston 



