I Vol. 2 



400 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



of every case of the hold-over blight, and this in great fruit 

 regions requires a small army of trained inspectors. During 

 the blighting period in late spring and early summer, if one 

 would save his orchard, the trees must be cut over for removal 

 of diseased material as often as every week, and in the worst 

 weather oftener. 



The introduction of diseases transmitted by way of seeds, 

 bulbs, and tubers may be avoided by obtaining these from 

 plants not subject to the disease. As this freedom cannot 

 always be known, bulbs and tubers should be inspected criti- 

 cally before planting, and firm-coated seeds should be soaked 

 for 15 minutes in 1 :1000 mercuric chlorid water. In case of 

 two plants (cabbage and maize) we know positively that the 

 diseases are transmitted on the seed and this is probably true 

 for several others — beans, sorghum, orchard grass. All 

 shrivelled seeds should be screened out before planting. 



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 new earth which one has good reason to 

 think free from the parasite in question. 



Nematode-infected soil should be avoided. 



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 in case of sugar-cane by Cobb, the more 

 intelligent cane planters in New South Wales have overcome 

 the disease due to Bacterium vascularum. 



On badly infested soils a careful long rotation should be 

 practised and the low places should be drained. 



Certain diseases may be held in check by germicidal sprays. 

 Pierce reduced the number of infections in walnut blight fifty 

 per cent by this method. Scott and Rorer combated leaf- 

 spot of the peach in this way, the sprayed trees retaining 

 their leaves, the unsprayed ones becoming defoliated. 



in Italy has recommended it and used it successfully on olive 

 trees following hail-storms to keep out the olive tubercle. 



When diseases are transmitted by insects the destruction 

 of the latter must receive prompt attention. 



