191 2.] Sterilisation of Soil for Glasshouse Work. 813 



191 1. The young plants took longer to come through in 

 the steam-sterilised soil than in the other soils. They made 

 best growth in the soil heated to 130 0 F., the difference 

 showing clearly by March 6th; a little later those in the soils 

 treated with toluol and carbon disulphide * began to go ahead,, 

 but not until three weeks had elapsed after sowing did the 

 plants in the steam-sterilised soil even catch up to those in 

 the untreated soil, and it was eight weeks before they began 

 to show any marked superiority. Flowers appeared first on 

 the plants grown in the soil heated to 130 0 F. and in the 

 steam-sterilised soil dressed with basic slag, and last on those 

 in the untreated soil. The plants on the treated soils not 

 only lasted longer, but produced much more fruit than those 

 on the untreated soil. Some of them are shown in Fig. 2. 

 The weights were : — • 







Partially sterilised by 





Un- 

 treated. 



Heat. 



Chemicals. 





20O° 



200° + 



basic 

 slag. 



1 30 0 



Toluol. 



Carbon 

 di- 

 sulphide. 



Relative plant weight, "1 

 dried (leaves, stems, I 

 &c, no fruit) ... ..J 



Relative weight of fruit ... 



Actual weight of fruit per) 

 plant (grams) .. ... J 



Fruit produced per 100) 

 parts of dry plant weight J 



100 



100 

 160 



7S0 



132 



342 

 546 



2,020 



123 



332 

 530 



2,110 



119 



339 

 540 

 2,220 



112 



366 

 5*5 

 2,540 



117 



346 

 553 

 2,300 



In this experiment the plants were not fed, our object being 

 to ascertain what the unaided soil can do after it has been 

 treated. It will be noticed that the extra growth of leaf is not 

 produced at the expense of the fruit, for we obtained much 

 more fruit per 100 parts of plant weight off the plants on 

 the treated than on the untreated soils. 



We do not wish to lay too much stress on the actual fruit 

 increase obtained, because there were only five plants in each 

 set, and fruiting is very much affected by details of man- 

 agement. We can, however, legitimately conclude that 



* At the rate of ^ per cent., i.e. I gallon per ton. 



