PARAFFINED WIRE POTS FOR SOIL CULTURES. 63 



In attempting' to use potted plants for studies of the relation 

 of soils to plant growth, whether the physical properties of the soil 

 or the chemical nature of the soil solution is under consideration, 

 this peculiar and undoubtedly abnormal growth of the roots has 

 always constituted a serious difficulty, for it is obviously unsafe 

 to assume that the behavior of such potted plants is the same as 

 would be exhibited had they been grown in the open. Indeed 

 it has been found in the laboratories of the Bureau of Soils of 

 the U. S. Department of Agriculture, at Washington, that if two 

 soil samples, one of an agriculturall}- poor soil and the other of a 

 good one, are placed in 3 or 4 inch pots and wheat is grown there- 



FiG. 10. 



in, the plants in the two pots fail to show the relative productive- 

 ness of the soils and are apt to be quite similar in the two cultures. 

 This is probably on account of the abnormal distributi(in of roots 

 described above. Roots of plants grown in common pots are not 

 entirely controlled by the soil conditions but are in an environment 

 quite foreign to soil in the open ; many of these organs have one 

 side closely applied to the wall of the pot, which is very dififerent 

 from the soil, and a large portion of them are living, if not prac- 

 tically in moist air instead of soil, at least in soil to wdiich an 

 abnormally great access of air is allowed. Thus the growth of 

 plants in these conditions should not be expected to exhibit anv 

 marked relation to the nature of the soil which fills the pot. 



A new form of pot which completely avoids the difficulties men- 



