10 



BULLETIN 1120, U. S. DEPABTMEFT OF AGRICULTURE. 



explains why no canker occurred in those portions of the rows of 

 young flax plants shaded by the vertical strips of canvas, while at 

 the same time some plants were cankered in the portions of the rows 

 not so shaded. 



6.30 /iM. 9.30 



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Fig. 2.— Diagram showing the variations in soil-surface temperatures in 

 different parts of plat C at Fargo, N. Dab., on July 18, 1919. 



Table 7 also shows that higher soil-surface temperatures occurred 

 where the heavy dark soil had not received a surface application of 

 light yellow sand. This probably explains why more canker occurred 

 in the portions of the plats where sand had not been applied, as 

 sho%vnby the data in Tables 2 and 3. 



On July 18, 1919, when the soil-surface temperature data shown 

 in Table 7 were taken, the sun shone brightly until 2.30 p. m., when 

 it became obscured by clouds. About 4 o'clock it began to rain. 

 Previous to this the soil was fairly dry. 



