164 



Plant Physiology 



The method has been much used in connection with 

 Livingston's plan of using transpiration as a measure of 



FIG. 48. The paraffin-basket method. Upper illustration shows se- 

 quence of stages in preparing cultures, and the lower a comparison of 

 root growth in a basket (left) with a tumbler (right). [Photograph 

 from the Bureau of Soils, U. S. Dept. Agl.] 



growth, but it has a much wider application, whatever 

 the indicator may be, in the general study of the mineral 

 nutrients of the soil, and many other soil conditions. 

 This method is unnecessary where the conditions of soil 

 moisture are constant, and with grades of coarse sand. 



