Fig. 39. — Steamed soil is a healthier medium for plant growth than untreated soil 

 infested by eel worm. The root labelled " untreated " shows the " knots " 

 caused by eelworm ; the other, labelled " steam," is free. 



Steamed soil Untreated soil 



Fig. 40. — Tomato plants from a large commercial nursery. 

 The left-hand one is grown in steamed soil, the right 

 hand one in the same soil unsteamed. 



[ To face p. 242. 



