1917] FIELD CROPS. 37 



The sources of error in field experiments with cotton are enumerated as 

 follows : Soil variation, especially below 1-meter depth, insufficient frequency 

 of observation whereby accidental episodes can not be distinguished from 

 normal sequences, fluctuation of single plants, heterogeneity of commercial 

 varieties, and normal physiological variations from day to day. 



Analyses of agricultural yield. — II. The sowing-date experiment with 

 Egyptian cotton, 1913, W. L. Balls and F. S. Holton {Phil. Trans. Roy. Soc. 

 London, Ser. li, 206 (1915), No. 3S3, pp. 403-^,80, figs. 18).— The experiment de- 

 scribed dealt \\Uh the yield obtained by planting Egyptian cotton at weekly 

 intervals from Febi'uary 15 to April 11, including nine planting dates. Five 

 plats were planted each week and each plat contained a check row of about 

 150 plants. Statistical records, which are appended in tabular form, were 

 obtained for the field germination, weekly height of the main stem, daily flower- 

 ing, and weekly ripening of bolls. 



It is concluded that the data derived from the work show the existence of an 

 optimum date for planting which appears to be constant, or practically so, from 

 year to year. It was found that plantings made before this date did not gain 

 the corresponding average which might be expected, and that they might be 

 even inferior. The result is explained by the assumption that some depressing 

 factor is brought to bear on the early plantings which has less effect on later 

 ones. This depressant factor is believed to be primarily an internal one in- 

 duced within the plants. In this connection the authors show that internal 

 water shortage leaves an after effect o:i the plant which can only be removed 

 slowly by a restoration of an ample water supply. It is stated that this effect 

 when severe may require the lapse of several weeks for its complete disappear- 

 ance and in some instances it may never be quite overcome. 



"It is probable that this after effect is due to the production of toxic excreta 

 in such cells as grow under deficient water supply. . . . The fall in the growth 

 rate of the main stem which takes place in Egypt after midsummer would seem 

 to be due to the same factor, reasserting itself as the sole controller of 

 growth . . . when the plants have grown so large that their closely packed 

 root systems are inadequate to meet the loss by transpiration. 



"The action of the depressant factor is essentially confined to a single group 

 of meristematic cells. Thus the growth of the main stem may be checked but 

 that of the younger flowering branches may continue, they having been de- 

 veloped from areas which did not produce the toxin, because they were not 

 growing at the time when the toxin-provoking conditions were operative." 



It is further concluded that the origin of this depressant factor can be attrib- 

 uted to the temperature of the soil, which is the only factor of the environment 

 whose seasonal fluctuations are practically uniform from year to year. 



Early and midseason potatoes at Wisley, 1915 {Jour. Roy. Hort. Soc. I^l 

 {1915), No. 2, pp. 290-304). — Descriptions are given of 107 varieties of potatoes 

 under trial. The varieties giving the best results were Duke of York and Mid- 

 lothian Early varieties ; General Joffre, Old Yellow Ashleaf, Sharpe Express, 

 Sir John Llewelyn, Stirling Castle, and Winchill Seedling, medium early varie- 

 ties; and Arran Chief, Great Scot, Stretton No. 20, and Wolfe Secundus, mid- 

 season varieties. 



Sugar beets for factory purposes, F. T. Shutt {Canada Expt. Farms Rpts. 

 1915, pp. 155-160). — The percentage of sugar and of solids in the juice of sugar 

 beets, the coefficient of purity, the average weight per root, and the yield per 

 acre are recorded for five varieties grown at the Dominion Experimental Farms 

 in 1914. The average percentage of sugar in the juice of sugar beets grown on 

 these farms from 1902 to 1914, inclusive, is also given in a table, and notes re- 



