44 



Development and Activities of Roots of Crop Plants. 



The weather for the most part remained cold and cloudy, but no frost oc- 

 curred. The water-content of the soil averaged about 30 per cent. The soil 

 temperatures remained low (minimum 52°, maximum 66° F., at a depth of 

 6 inches). Air temperatures, recorded by a hygrothermograph, appropriately 

 sheltered and placed with the recording appa- 

 ratus 4 inches above the soil surface in an 

 adjacent prairie, gave an average day reading 

 of about 63° F., while the average night tem- 

 perature was only 53° F. The relative humidity 

 was high. 



Rotmistrov (1909 : 34) states that at the end 

 of 21 days after the appearance of the sprout, 

 not only was the extreme breadth of the root 

 system marked off, but the depth of penetra- 

 tion reached 0.5 meter and roots of the third 

 order were clearly visible, the whole 

 forming a felt-like entanglement. 

 Clearly our plants were developing 

 more slowly. However, oats planted 

 May 4, and examined 26 days later, 

 were further developed than 45-day- 

 old plants just described. They were 

 5 inches high, had 5 leaves each, and 

 some had tillers. The root growth 

 was proportional. It is interesting 

 to note also the more rapid root 

 penetration of White Kherson oats 

 in the loess soils at Peru. Here 

 plants only 14 days older than those 

 just described had extended their 

 roots into the fourth foot of soil. 



Fifteen days later, on May 30, the 

 root development was again studied. 

 During this period both roots and 

 shoots had grown rapidly. Although 

 the soil remained quite wet (25 to 30 

 per cent water-content), it was con- 

 siderably warmer, the average daily 

 temperature during the last week of 

 May reaching 71° F. at a depth of 6 

 inches. This was higher than the 

 average air-temperature (65° F.) for 

 the same interval. Fewer rains and 

 less cloudy weather occurred during 

 this last half of the month, although 

 the humidity remained high. 



The average height of the plants was about 9 inches, but some were 3 inches 

 taller. Each plant had 7 to 9 leaves, one or two of the oldest ones being 

 either dead or rapidly deteriorating. About one-tenth of the plants had 



Oata 60 days old. 



