igi2.] Sterilisation of Soil for Glasshouse Work. 817 



root, as seen in Fig. 5. The effect is not easy to explain, 

 and is not shown to nearly so marked an extent in soil 

 heated to 130 0 F., although at this temperature eelworms 

 and other pests are killed, while it is scarcely shown at all 

 in soils treated with toluol and carbon disulphide. But 

 steamed soil is a very useful medium for plant growth 

 wherever good fibrous root development is wanted. 



The Appearance of the Plant. — Plants grown on steamed 

 soils show, in comparison with those on untreated soils, 

 larger leaves, stouter stems, a darker green colour, shorter 

 joints, and a more compact vigorous habit. The actual 

 amount of shortening of the joints depends on the plant ; it 

 was not noticeable in our tomatoes, but was very distinct in 

 the chrysanthemums, and we have observed it in cucumbers ; 

 it is very marked in our outdoor experiments with rye, 

 mustard, &c. 



In spite of the extra growth on the steamed soils the plant 

 is not rank or coarse, a result we attribute to the nature of 

 the food it is now taking up. It flowers earlier and produces 

 a greater quantity of fruit than others on untreated soils, 

 excepting, of course, where the difference between the soils 

 has been swamped by liberal manuring. 



Quality of Fruit. — In the case of tomatoes and cucumbers, 

 the only fruits we have as yet studied, the quality of fruit 

 is better on the steamed than on the untreated soil. During 

 the present season cucumbers grown on heated soils in a 

 large commercial glasshouse have shown a marked improve- 

 ment in quality, although there was no noticeable increase 

 in quantity, which indeed is probably already a maximum 

 for the general conditions. Our own tomatoes were sent to 

 an expert of irreproachable taste and judgment, who arranged 

 them as follows : — (1) From toluol-treated soil, finest in 

 flavour; (2) from steamed soil, very good, sweet; (3) from 

 untreated soil, poorest in flavour.* 



Leguminous Plants. — As is well known, leguminous plants 

 differ from others in the manner of their nitrogen nutrition, 



* A grower who now partially sterilises soil on a large scale has kindly , offered 

 to put on rail a cart-load or truck-load of steamed soil at a nominal charge in order 

 that anyone interested may try the effect of such soil on plant growth without having 

 to put up a steriliser. We shall be happy to put anyone into communication with 

 this gentleman. 



