48 



rains warm the soil ; on the other hand, autumn rains apparently 

 prevent the soil from cooling- as much as it would otherwise have 

 done. 



There is no satisfactory substitute for a recording- soil 

 thermometer, but a fair estimation of the mean daily temperature 

 at the Gin. depth can be obtained over the greater part of the year 

 by regarding- the maximum air temperature as the maximum soil 

 temperature, and the 12in. depth soil temperature at 9 a.m. as the 

 minimum, and then taking- the mean. 



The relations between the daily temperature rise in the soil 

 and the air have been studied in detail by following the (^hanges in 

 the ratio **"" -''"''^'■'"'le fy^)J^•^ ^],^y (,, ^\.:^y^ These ratios fall into :i 



air amplitude 



well-defined fref|uency cur\e whose maximum occurs between the 

 values .2 — .3. This range of the ratio is prevalent in spring 

 and early summer, and also in earh autumn. A similar curve is 

 given by the ratios of the daily (X)oling^ of soil and air, the maximum 

 in this case being- between .3 — .4. The ratio Vir anTpTiululT of course 

 alters \\hen either, or both, numerator and demominator change. 

 A series of relations between these changes, both for indix idual and 

 a\'erag-ed values is g-i\ en in the paper. 



XX\TTT. E. A. Fisher. " Studies on Soil Reaction — /. A 

 resume.'' journal of Agricultural vScience, 1921. 

 Vol. XI. pp. 19-44. 



A critical account of the various hypotheses put forward to 

 explain the phenomena of soil acidity and the methods that have 

 been sug-g-estcd for estimating it. All present methods are shown 

 to be defecti\"e. The hydrc^gen ion concentration gi\es useful in- 

 dications, but the titration methods, lime requirement methods, 

 etc., are defective because the lime requirement is really very com- 

 plex, being- made up of two factors; the lime required to neutralise 

 soil acids, and the lime actually absorb(,'d by the soil. It is im- 

 possible at present to differentiate these or to compare with any 

 deg-ree of stri(^fness one soil or one base with another. 



XXIX. E.A.Fisher. '' Studies on Soil Reaction — 77. riie 

 coiorimetric deterniination of the Jiydrofren ion con- 

 centration in soils and aqueous soil extracts/' 

 Journal of Agricultural vScience, 1921. Vol. XI. 

 pp. 45-65. 



Details to be observed and difficulties to be overcome in the 

 coiorimetric determination o( the hydrog-en ion concentration in 

 soils. It is shown that the fineness of division of the soil is of (X)n- 

 siderable importan(x\ 



PLANT PATHOL()(i\ . 



XXX. A. D. Imms and M. A. Husain. " Field Experi- 



}nc}its on the (liemotropic Responses of Insects." 



Annals of Applied Biologv, 1920. Vol. VI. pp. 



269-292. 



During^ the (M)urse of these experiments the insects attracted 



consisted almost exclusi\ely of Diptera ; Heniiptera, Coleoptera 



and Neuroptera were unrepresented. A small number of Noctuid 



Lepidoptera entered the traps, which however were not adapted for 



such relatively large insects as many Lepidoptera. Beer, cane 



molasses, and mixtures of these two substances are powerful 



