April 16, 1920] 



SCIENCE 



393 



ment is expected to pay about half tlie cost of 

 the system. 



. There are now about 9,000 superannuated 

 civil servants, most of them in Washington. 

 They ■will go out in a body. The retired list 

 ■will eventually reach about 30,000. But ■with 

 the moderate annuities allo^wed, the maximum 

 being $720, the government's experiment ■will 

 cost little. The efficiency of the working force 

 will be increased. More work ■will be done by 

 a smaller staff. — New Yorh Tribune. 



THE ECOLOGICAL RELATIONS OF 

 ROOTS! 



Professor J. E. Weaver has recently put 

 out an extensive study on roots which com- 

 prises observations made in the " prairies of 

 eastern Nebraska, chaparral of southeastern 

 Nebraska, prairies of southeastern Washing- 

 ■ton and adjacent Idaho, plains and sandhilla 

 of Colorado, the gravel-slide, the half-gravel- 

 slide, and forest commimities of the Rocky 

 Mountains of Colorado." The roots of about 

 140 species are described. The species in- 

 clude shrubs, grasses and other herbs. With 

 a description of the roots is presented a char- 

 acterization of the physical environment. 

 Among other features of the latter are given 

 the rainfall and evaporation, the temperature 

 of the air and to a certain extent the tem- 

 perature of the soil and its moisture content. 

 The work is abundantly illustrated with root 

 maps and reproductions of photographs. 



The study by Weaver is a continuation and 

 an extension of his well-known work along 

 similar lines. It is wholly observational and 

 must be considered as constituting a very 

 noteworthy contribution to o'ur knowledge of 

 the habits of roots. It touches elbows ■with 

 so many features associated with the habits 

 and relations of the plants of the regions 

 studied that it is not practicable to present a 

 summary of the results. However, it may 

 not be amiss, to point out certain of the more 

 interesting of the facts presented. For de- 

 tailed information the reader is referred to 

 the work itself. 



1 Oamegie Institution of "Washington, Publica- 

 tion No. 286, 1919. 



Without attempting to summarize exactly it 

 can be said that in a general way the root 

 systems of plants in the communities studied 

 are fairly characteristic. Thus in the prairies 

 and the plains also the roots usually extend 

 widely and penetrate deeply, but more deeply 

 in the former than in the latter community. 

 And the tap root is the principal feature. 

 In the sandhills the roots of several species 

 are confined to the surface 2 feet, and prac- 

 tically all show a striking " profusion of long, 

 ■widely spreading laterals in this surface-soil 

 stratiun." In the gravel-slide and forest com- 

 munities of the Rocky Mountains, adjoining 

 Colorado Springs, the roots are confined to 

 the surface 18-24 inches. In the half-gravel- 

 slide, however, the root penetration is deeper, 

 although the root systems develop ■widely 

 spreading shallow roots as well. Finally, in 

 the case of species growing in more than one 

 habitat it was found that in most cases the 

 direction and extent of roots developed corre- 

 sponded very well to the " community root 

 habit." 



Roots of different species may be so unlike 

 in the extent and direction of their develop- 

 ment, as well as in other morphological 

 features, as to be readily identifiable. They 

 also imdoubtedly exhibit quite as distinct 

 physiological characteristics, although such 

 can not be told from inspection. For these 

 reasons a knowledge of the roots of any 

 habitat gives a very good clue to many of 

 the striking features of that habitat, just as 

 the nature of the shoot of a plant reveals 

 much regarding the subaerial conditions un- 

 der which it has developed. It consequently 

 follows that through the study of roots of 

 native plants, much can be learned in ad- 

 vance of culture of the possibilities of agri- 

 cultural lands. Such, however, is a possible 

 economic application of this and similar root 

 studies and was suggested, but not developed, 

 by the author. 



The most striking root figure by Weaver is 

 that of Ipomcea leptopJiylla of the sandhills 

 about forty miles southeast of Colorado 

 Springs. The soil absorbs all of the rain and 

 there is practically no run-off. Through a 



