SOIL CONDITIONS AFFECTING PLANT GROWTH 



35 



ence between sustained growth and the individual processes of 

 assimilation, etc. In the classical experiments of F. F. Black- 

 man and of Miss Matthaei (now A. G. L. Howard) (193) the 

 effect of temperature on assimilation, all other factors being 

 eliminated, was precisely that obtaining in an ordinary chemi- 

 cal reaction ; so also for respiration. Miss Matthaei found that 

 the amounts of carbon dioxide assimilated by a cherry laurel 

 leaf per 30 sq. cms. (about 8 sq. ins.) per hour at various 

 temperatures were : 



By interpolation, the values at o, 10, 20, etc., can be found, 

 and the rate of assimilation is thus seen approximately to 

 double for every increase of 10, the usual order of increase in 

 chemical reactions : 2 



But on the other hand, the effect of temperature on the rate 

 of growth of a plant as a whole is in no wise like its effect in 

 accelerating chemical change. Bialoblocki's (37) results with 

 barley were as follows : 



The two curves are shown in Fig. 3 ; the difference between 



J The rates were maintained only for a short time at the higher tempera- 

 tures. 



2 A list of the papers dealing wijth the temperature co-efficient for cell growth 

 is given in Science, 6th November, 1908. See also Zaleski, W., Ber. Deut. Bot. 

 Ges., 1909, 27, 56-62. 



3* 



