September 8, 1922] 



SCIENCE 



283 



no doubt had an important part in shaping the 

 topography of the region, wliieh may be de- 

 scribed as the level to rolling 'bottom of an 

 ancient lake or arm of the sea dotted with 

 sandy knolls or modified sand dunes. The 

 shifting also presents to the farmers of the sec- 

 tion some problems of soil management. 



Probably the most striking instance in recent 

 years of wind erosion of soils in this vicinity 

 occurred on the days of April 27 to 30, 1922. 

 Observations by the writer showed a drift as 

 deep as three inches, the deepest observed being 

 on the south sides of tobacco barns. Onion 

 seeds were blown out of the soil necessitating in 

 some cases reseeding, and no doubt many tons 

 of fertilizer were carried from recently fer- 

 tilized onion fields on which a first application 

 of one ton of high grade fertilizer is the com- 

 mon practice. It was observed that any sort of 

 a ground covering, even loose tobacco stalks, 

 was rather effective in cheeking erosion, but a 

 growing cover crop as commonly used in 

 tobacco, but not onion, fields was most effective. 



The winds most disastrous from the stand- 

 point of soil erosion are those of two or more 

 days' duration, the first day usually being re- 

 quired to dry the soil. Although sandstorms 

 may occur frequently during the year, the most 

 damage is done in the spring when the land is 

 being or has been recently prepared for crops. 



A. B. Beaumont 

 Amherst, Mass. 



SCIENTIFIC BOOKS 



Development and Activities of the Boots of 

 Crop Plants: A Study in Crop Ecology. 

 By John E. Weaver^ Frank C. Jean and 

 John W. Crist. 17 s 25 em., VI + 117 

 pages, 42 figures, 14 plates. Carnegie Inst. 

 Washington, Pubh no. 316. May 11, 1922. 



Students of plants, especially in physi- 

 ology, ecology and agriculture, will be inter- 

 ested in Weaver, Jean and Grist's book on the 

 roots of crop plants, in which is brought forth 

 a mass of detailed information in a field that 

 has been largely neglected until recently. The 

 studies now reported are a continuation of 

 those presented in Weaver's "Root Develop- 



ment in the Grassland Formation" (1920). 

 Much of the present work follows the meth- 

 ods of his earlier investigations on the fonn 

 and distribution of the root systems of un- 

 cultivated plants. The descriptive data are 

 obtained by what must seem to most botanists 

 very tedious and laborious excavations; each 

 root is traced to its end and the size, form, 

 etc., of the whole root system of each plant is 

 shown diagrammatieally on a chart. The pub- 

 lished charts frequently show the size of the 

 top, as well as the depth and spread of the 

 root system and the num'ber of roots. Root 

 systems of plants growing under field con- 

 ditions are described, in several stages of their 

 development, for Lincoln and Peru, Nebraska, 

 for Phillipsburg, Kansas, and for Burlington, 

 Colorado, these stations having mean annual 

 precipitations of about 33, 28, 23 and 17 

 inches, respectively. The plants dealt with 

 are: oats, wheat, barley, maize, potato, alfalfa 

 and sweet clover, for the seasons of 1919, 1920 

 and 1921. Some excellent experimental studies 

 bearing on the soil-depths from which water 

 and nitrate were removed during several de- 

 velopmental stages of the plants are con- 

 sidered in the final chapter of the book. 



It is pointed out that the root systems of 

 crop plants show modes of growth similar to 

 those of native plants growing in the same 

 region, both being apparently influenced by 

 the environmental moisture conditions. With 

 higher evaporation intensities and drier sur- 

 face soils the root systems tend to be developed 

 less extensively in the superficial soil layers 

 and they extend farther into the deeper layers. 

 There are some differences between the different 

 forms of plants, but all the forms studied usu- 

 ally have, at the approach of maturity, a set 

 of roots that ramify laterally in the upper 

 30 or 40 cm. of soil, and a set that reach down- 

 ward, with more or less profuse branching, to 

 depths of from 1 to nearly 3 m. The two por- 

 tions of the root system may be relatively dis- 

 tinct or they may be nearly continuous. The 

 deepest soil layers reached are of course not 

 generally well occupied by branches. 



The authors emphasize the fact that the 

 roots of crop plants usually penetrate and 



