1912.] Sterilisation of Soil for Glasshouse Work. 8ii 



stances present in the soil ; the plant, therefore, develops 

 rather differently than before; 



(3) disease germs, weeds, &c, are killed. 



For some time past we have been conducting experiments 

 in our own and other glasshouses, and we propose in this 

 paper to set out our results, to describe methods of partial 

 sterilisation that can be carried out in practice, and more 

 especially to describe the objects to be attained, so that the 

 grower who feels that he can cheapen the methods shall 

 know the nature of his task. 



The Effect of Partial Sterilisation on the Food Supply 



of Plants. 



Two cases arise in greenhouse practice : (a) the plant is 

 put up in a suitable compost and left without much added 

 manure; (b) it is regularly and heavily (often excessively) 

 manured with a variety of substances. Only in the first case 

 is adequate use made of the extra food obtained by partial 

 sterilisation ; where large quantities of food are already added 

 it is obviously useless to look for any benefit by adding more. 



(a) Plants grown in compost, but not frequently manured: 

 Chrysanthemums. — Mr. H. Burton Tate having very kindly 

 allowed us access to his Harpenden glasshouses, we divided 

 the compost into which the chrysanthemum cuttings were to 

 be struck into three parts, heating one by steam to 

 200-2 1 o° F., treating another with toluol (J per cent.), and 

 leaving the third untreated. The compost was made up in 

 the usual way by the head gardener, who also took the 

 cuttings and carried the plants through as in the ordinary 

 practice of a good private glasshouse. The cuttings were 

 put in on December 5th, 19 10, and were all found to strike 

 at about the same time, no consistent differences being 

 observed. They were potted up on March 10th, 191 1, when 

 it was noticed that the plants in the untreated soil had made 

 rather better roots than the others. The plants were then 

 transferred to a cold frame. Before long those in the treated 

 soil began to go ahead, and on July 13th, when the photo- 

 graphs given in Fig. 1 were taken, they had larger leaves, 

 stouter stems, shorter internodes, and generally a sturdier 

 and altogether more promising aspect than those on the 



3 K 2 



