400 



BOTANICAL GAZETTE 



[DECEMBER 



At least two or three times during the course of the experiments, 

 which extended from September 191 7 to May 1918, the seal was 

 broken and the soil thoroughly aerated by means of an aspirator. 

 An examination of containers discarded from time to time because 

 of accidents to the aerial parts of the plants showed that at all 

 times the soil was sweet and in good condition. Such an examina- 

 tion also revealed that the roots of both deciduous and coniferous 

 trees had penetrated somewhat into the new soil. As pointed out 

 by MacDougal (14), the root growth of broad-leaves corresponds 

 to the warm periods during which absorption is active, while any 



Fig. 2. — Battery of 3-year-old yellow pines; photographed February 28, 1918; 

 none of needles fallen. 



possible resting period in summer is deemed due to scarcity of 

 water and not to any inherent tendency of the plant toward a 

 periodicity in growth. 



Pinus ponderosa 



Eight 3-year-old seedlings of yellow pine were repotted, as 

 already described, into the metal containers 5 . 5 inches in diameter 

 and 14 inches deep, and the first weighings were made on September 

 24. This battery is shown in fig. 2. The total leaf area was deter- 

 mined for several of the plants the following spring and at the end 

 of the experiment. This ranged from a minimum of 2 . 905 sq. dm. 

 in plant no. 7, to a maximum of 6.428 sq. dm. in plant no. i 



