PLATE XXXVIII 



Fig. I. — Method used in isolating root systems in the field. View of two soil prisms 

 ready for washing. The trenches here shown are 3 feet wide, 12 feet long, and 6 feet 

 deep. 



Fig. 2. — Method used in isolating root systems. This figure shows the method of 

 placing the cross wires through the soil block. 



Fig. 3. — Method of washing used in the isolation of the root systems. The trench 

 was partially filled with water, which was continuously pumped upon the prism of 

 soil by means of a pitcher pump. 



(332) 



