FIELD CROPS. 229 



leads to an injury or a complete breaking off of either the cotyledons or radicle. 

 Brick dust, which allowed for too rapid evaporation, was not suitable for this 

 work. 



The number of seeds whose seed coat became thus fractured within 10 days 

 ranged from 7 to 9.75 per cent. With an extension of the period of germination 

 the percentage of fractured seeds became less. 



It is noted further that seeds taken from the filter paper just as the germ 

 pricked the seed coat and placed in garden soil in pots showed a very much 

 lower percentage of fractured seed coats and consequently fewer crippled 

 plants. 



The author notes that herein lie variations and discrepancies in reports of 

 germination tests in general, inasmuch as the seed is left to lie undisturbed in 

 nn unfavorable moisture condition. In sowing the seeds in soil it was found 

 that the optimum conditions for germination as found in the artificial seed tests 

 did not exist and that seeds with fractured seed coats or otherwise weakened 

 germs could scarcely survive. 



The effect of weather upon the yield of com. J. W. Smith (Mo. Weather 

 Rev., 42 (WlJf), No. 2, pp. 78-87, figs. //).— On the basis of the assumption that 

 there is a critical period in the gi-owth of every crop during which the weather 

 conditions exert a determining influence upon the yield, the author conducted 

 a series of studies, the results of which in regard to the corn crop are here 

 given as follows : 



" The controlling weather factor in the great corn-growing districts of the 

 T^'nited States is rainfall. The critical period of growth of com during which 

 favorable weather will cause a large crop and vnifavorable weather a short crop 

 is comparatively brief. If the rainfall for calendar months he considered, that 

 for July has a far greater elTect uijou the corn yield than rainfall for any 

 other month. The rainfall from about the niiddle of July to the middle of 

 August has a far greater effect upon the corn yield than that for any other 

 period of similar length. The rainfall for the 10 days following the date of 

 blossoming has an almost dominating effect upon the yield of corn, the larger 

 the rainfall the larger the yield. 



'* If the rainfall is small during the 10 days after blossoming a high temper- 

 ature has a very unfavorable effect upon the yield. Rainfalls of one-half inch 

 or more have a greater eft'ect upon the development of corn than falls of less 

 amount. It seems possible to give a close estimate of the probable yield of 

 corn by August 10, by careful study of the weather conditions that have pre- 

 vailed up to that time. 



" The importance of shallow cultivation after each rainfall in July and after 

 August 1 for the purpose of forming a dust mulch and thus preventing the loss 

 of water bj' evaporation can not be overestimated. The science of agricultural 

 meteorology can be advanced, and the results of these investigations be made 

 of more practical value to the farmer, by a detailed study of the critical periods 

 of growth and the weather factors most affecting the yield of other field and 

 garden crops." 



The frequency of low temperatures in the Sudan and its effect on the cot- 

 ton crop, H. E. Hurst (Cairo Sci. Jour., 7 (1913), No. 87, pp. 265-268, pi. 1).— 

 This article gives tabulated data and discusses the frequency of low temper- 

 ature in certain districts as a preliminary to research work on the effect on the 

 cotton crop. 



The effect of water on the cultivation of cotton, H. T. Ferrab and H. E. 

 Hurst (Survey Dept. Egypt Paper 24 (1912), pp. VIII+53, pis. i).— In study- 

 ing by means of bore holes the relation between the height of the water table 

 or level of the subsoil water and the yield of cotton, it was found that there 



