3i6 Journal of Agricultural Research voi. vi, no. 9 



taining the plants whose root S3^stems are desired and then placing over 

 this block of earth a wire cage of such a shape and size as to fit closely to 

 the vertical sides of the block. Numerous small wires are then run 

 through the prism of earth and fastened to each side of the cage. The 

 plants are fastened to the cage at the surface of the soil and the roots 

 washed free from dirt by means of a stream of water. When the earth 

 is washed away, the main roots remain suspended on the cross wires in 

 the same position that they occupied in the soil. 



This method is open to criticism, first, because in order to use it with 

 any degree of satisfaction the prism of soil must be limited to about 18 

 inches in thickness, and on this account one obtains only a section of the 

 root system. Furthermore, the main roots of the plant may not be in the 

 prism of soil which has been isolated; therefore, when the soil is washed 

 away, only a poor representation of the root system is obtained. Finall}^ 

 although the primary roots of the plant remain on the wires in the same 

 position that they occupied in the soil, it is impossible to retain all the 

 finer roots in their normal position. No method has been devised, so 

 far as is knovv^n to the writer, whereby the root systems of mature plants 

 growing in the field under natural conditions can be isolated intact. 

 The method of Rotmistrov (6) for obtaining complete root systems is 

 open to criticism because root systems certainly would not develop 

 normall)^ in so small a volume of soil. For a comparative study of the 

 general nature of the root systems of plants, growing under field condi- 

 tions, the modified method of King as used in these experiments seems 

 to be the least objectionable. 



In the work reported in this paper, sections of the root systems were 

 obtained crosswise of the rows. The prisms of soil varied from 15 to 18 

 inches in thicl^ness and were isolated by digging a trench 2% feet wide 

 around them. After the isolation of a prism of soil, a wooden frame- 

 work of light material was fitted snugly over it. Ordinary wire fencing 

 with a 4- to 6-inch rectangular mesh was placed on tvv-o sides of the frame- 

 work (PI. XXXVIII, fig. 1,2). This was found to be much more sat- 

 isfactory than the poultry netting used by King and Ten Eyck, since 

 the small mesh of such netting made it impossible to photograph the root 

 systems with any degree of satisfaction after they had been isolated. 

 The plant stubs and root crowns were held in place by wiring them to 

 narrovv^ strips of inch boards which were placed crosswise of the soil 

 block at the surface of the soil and nailed to both sides of the framework 

 of the cage. This method is much more convenient and simple than the 

 one used by King (5) and Ten Eyck (9, 10, 11). In order to hold the 

 plants in place, these investigators removed the upper portion of the 

 soil surrounding the crown of the plant, and replaced it by a plaster of 

 Paris cast. 



For cross wires, ordinary broom wire was found to be the most satis- 

 factory. Owing to the compactness of the soil, a X"inch iron rod pointed 



