204 



Bulletin 80 



and in feeding capacity. Individual roots are coarse, covered 

 with thick epidermis, and are abruptly angular, apparently as 

 a result of chemotropic contortions. Root tips are shortened and 

 thickened and in some instances are strongly proliferated. The 

 anatomical structures associated with these changes in form are 

 very striking. In corn the cells of the primary cortex, in normal 

 roots, are elongated parallel with the axis of the root, and in 

 longitudinal tangential section measured about 74 by 30 microns. 

 Injured cells of corn grown in soil containing 0.1 per cent copper 

 gave longitudinal tangential sections approximately 34 by 30 

 microns, as shown on accompanying drawings. (See, also, plates 

 II, III, and rV. 



U 



HUn 



--- 



)-* 



u-i 



>- 



~ 

 ^ 



^ 



u 



a b 



Fig. 14. — a. Tangential longitudinal section of corn root grown in soil 

 containing .1 per cent of copper as copper sulpliate, showing cells of cortex 

 of injured rootlet, b. Tangential longitudinal section of normal corn root 

 cells of cortex. (X ± 300 diam.) (Sections by G. F. Freeman.) 



These structural moditications, taken in connection with other 

 symptoms and conditions and in the absence of other causes, 

 such as an excess of alkali salts, ** confirm a diagnosis for copper 

 injury in a soil of doubtful toxicity. For instance, March 4. 

 1916, two sets of samples of barley were collected in the district 

 studied, and the material examined for evidence of copper in- 

 jury, as follows : 



Lot 1. — Young barley plants from the upper end of a field midway 

 between Safford and Solomonville, under Montezuma Canal. The soil next 

 the ditch shows old tailings, and there are irregular areas of yellow 

 barley immediately under the canal. 



9 See Livingston, Botanical Gazette, vol. 30, no. o, p. 229, 19O0. 



