March, 1922. 



SCIENTIFIC AGRICULTURE 



227 



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rig 2 Germination of Poo compressa (L) 



ShovMing h^mporoture chanqes in light experiment 



Influence of Fluctuating Temperatures. 



Simultaneously with the above tests an- 

 other experiment was conducted for the 

 purpose of comparing the effect of ap- 

 proximately steady temperatures with fluc- 

 tuating temperatures of different ranges 

 and exten't.s of range. The same twelve 

 samples were used, and for eacih test 

 two hundred seeds were taken indiscrimin- 

 ately from each sample. The seeds were 

 placed on the surface of soil which was 

 kept moist by sprinkling throughout the 

 period of the test. Five standard dark 

 germinators were used. Adjustments of 

 heat conditions were so made that these 

 germinators maintained approximately 

 steady temperatures of 16 deg. C, 25 deg. 

 €., 30 deg. C. and 35 deg. C. respectively. 

 A set of seeds from each of the twelve sam- ' 

 pies was placed in each of these germin- 

 ators and kept there continuously for 

 thirty-five days, this being the period of 

 time allowed for the experiment. In this 

 way provision was made for the tests being 

 carried out at the different steady tem- 

 peratures above mentioned. In these ger- 

 minators, by changing tests from one to 

 another, the following temperature fluc- 

 tuations were also provided : 16 deg. C, to 

 20 deg. C. ; 16 deg. C. to 25 deg. C. ; 16 deg. 

 C. to 30 deg. C. ; 16 deg. C. to 35 deg. C. ; 

 20 deg. C. to 25 deg. C. ; 20 deg. C. to 30 

 deg. C. ; 20 deg. C. to 35 deg. C. ; 25 deg. C. 

 to 30 deg. C. ; 25 deg. C. to 35 deg. C. ; and 

 30 deg. C. to 35 deg. C. Sets of seeds re- 

 presenting the twelve samples were pre- 

 pared for transfer according to the range 

 and extent of range of fluctuation desired. 



The transfers were made so that the sam- 

 ples were subjected to the higher temper- 

 atures from 9 o'clock a.m. until 5 o'clock 

 p.m. of the same day and remained at the 

 lower temperatures during the remainder 

 of the twenty-four hours. 



Figure 4 is a representative section of 

 the curves intended to illustrate the tem- 

 perature changes to which all of these tests 

 were subjected. The five approximately 

 horizontal lines, numbers 1, 2, 3, 4 and 5, 

 represent the five steady temperature 

 changes. For example, the lowest, uum- 



