conspectus: methods of control 73 



The seed bed in case of tobacco, tomato, cabbage, and trans- 

 planted plants generally, should be made on steam-heated or 

 fire-heated soil, or on new earth which one has good reason to 

 think free from the parasite in question. 



In the greenhouse, nematode-infested soils should be avoided 

 or steamed or drenched with formalin water (one pint of forma- 

 lin to 40 gallons of water). 



Cuttings of carnations, chrysanthemums, roses, peaches, 

 plums, apples, quinces, sugar-cane, etc., used for slips, buds, 

 or grafts should be from sound plants. By following this 

 practice, recommended by Cobb, the more intelligent sugar-cane 

 planters in New South Wales, it is said, have overcome the 

 disease due to Bacterium vascularum. 



Commercial growers of hothouse roses in Maryland, New 

 Jersey, New England and Canada have been much troubled 

 in recent years by crown gall. To avoid this disease in houses 

 great care should be exercised in the selection of soil and of 

 cuttings. A knife used on diseased roses must not be used again 

 on sound plants until disinfected. When a soil has become in- 

 fected it may be steamed under weighted sheet-iron pans for an 

 hour at 65 pounds pressure, by use of the autoclave (Fig. 56), 

 by the steam-chamber (Fig. 57), or by means of a steam-drag 



Fig. 51. — Braun's imbibition experiments with seed wheat to prevent injury 

 when subsequently treated with germicides. Formalin in distilled water O'ioo) 

 was used but the same results have been obtained with copper sulphate in water 

 (1:80) and with formalin water (M2o)- In each pot 100 seeds were used: 



VIII. Fulcasler wheat, planted March 8, 1918: photographed March 14. 



A. Soaked in formalin-water for 10 minutes (the usual method), then covered 

 for 6 hours to get penetrating effect of the formalin vapor. Pot shows much re- 

 tardation and killing. Germination 68 per cent. 



B. Check. Germination 85 per cent. 



C Seeds presoaked, then treated with formalin as in A. By "presoaking"' is 

 meant that the seeds were phmged into water for 10 minutes, then removed 

 and covered for 6 hours to keep moist. Germination 81 per cent. Plants show 

 stimulation. 



A". Poole wheat, planted March 20, 1919; photographed March 26. 



A. Seeds presoaked (10 minutes in water) then covered 6 hours to keep moist. 

 Treated 10 minutes in formalin-water, removed and covered for 6 hours. Then 

 planted. Pot shows stimulation and 86 per cent, germination. 



B. Check; 95 per cent, germination. 



C. Duplicate of A. Shows stimulation and 89 per cent, germination. 



