816 Sterilisation of Soil for Glasshouse Work, [jan., 



ample, Sutton's Ai recovered in four weeks, while Ring- 

 leader took five weeks. It commonly happened that recovery 

 was delayed till after the third and fourth leaves were out. 



Figs. 3 and 4 illustrate the two common cases ; in Fig. 3 

 steam-sterilisation has produced some condition detrimental to 

 the young plant which was not produced at a temperature 

 of 130 0 F.; in Fig. 4, however, the harmful effect had passed 

 off very rapidly. There was no obvious reason for the differ- 

 ence. 



Soon after the new leaves are out the retarded plants 

 make more rapid growth and soon catch up the plants 

 on the untreated soil, and, if no manure is being given, 

 pass them. The retardation therefore need cause no anxiety, 

 but it is an undoubted disadvantage, and is receiving careful 

 investigation. 



Fungus Development. — Some of the products formed by 

 heating rich soils to 200 0 F., or more, are very favourable 

 to the development of certain fungi, and if any of their spores 

 happen to be about (as is usually the case) a rapid growth 

 of mycelium begins in the surface layer, followed by a crop 

 of small, yellowish, saucer-like fructifications. The fungus 

 then disappears, and is not seen again ; it causes no injury 

 to the plant so far as we have been able to observe, but while 

 it lasts it sometimes binds the surface of the soil so solidly 

 that the young plant may have a difficulty in getting through. 

 The common form in our experiments was a Rhizina, prob- 

 ably R. inflata; it did not occur to any marked extent on 

 the soils heated to 130 0 F. or treated with toluol or carbon 

 disulphide. 



Root Action. — The root action is sometimes, but not 

 always, retarded in the early stages of growth in soils heated 

 to 200 0 F. Like the retardation of germination, the effect is 

 erratic. The same grower has obtained in August a good 

 root development, and in January a very poor one, in heated 

 soils. This problem also is under investigation with the 

 view of discovering a remedy. 



Later on, however, the soil heated to 200 0 F. stimulates 

 root action in a most remarkable way. Applied as a top 

 dressing to pots containing tomato plants or to borders where 

 cucumbers were growing, it caused a rapid growth of fibrous 



