DISEASES OF PLANTS. 649 



virulence. A disease believetl to be clue to .1/. sdcchari lias also been found on 

 Guinea corn, imphee, and sweet potatoes. 



This disease is not so prevalent on su^ar cane on land on which cotton has 

 bee.i srown previously, although in some instances the cane on such land has 

 been severly attacked, this beinj; due. it is thought, to the use of infected farm- 

 yard compost. In fields which have been allowed to lie fallow the disease exists 

 in an inverse ratio to the len.uth of the fallow period, the shorter the period 

 the gi'eater the amount of disease being present. 



Notes on the mosaic disease of tobacco, Perreau (Bui. Soc. Bot. France, 56 

 (1909), Xo. 1, pp. 53-55). — Attention is called to the appearance of this disease 

 in a field of tobacco growing on land which for 30 years had had no tobacco 

 on it. The disease was probably introduced either by means of the seed or by 

 the debris of leaves, capsules, etc., intermingled with the seed. 



By the use of seed from disease-resistant plants grown on laud free from 

 infected leaves, stems, etc., plants were produced which were practically free 

 from the disease, thus confirming the previous statement (E. S. R., IG, p. 677) 

 that by the proper selection of resistant varieties of tobacco this disease can be 

 controlled. 



Rust and smut resistance in wheat and smut experiments with oats and 

 maize, D. McAlpine (Jour. Dept. Agr. Victoria, S (1910). Ao. 5, pp. 2S.'f-289). — 

 In experiments on rust resistance in wheat, 21 varieties of wheat were used 

 and other species or subspecies of Triticum, viz, einkorn (T. monococcum), 

 emmer (T. sativum dicoccmn), spelt (T. sativum spelta), and Polish wheat 

 (T. polomcum). 



Of the 21 varieties tested only 1 was absolutely rust free, viz, Rieti, a French 

 bearded variety, and 5 practically free, viz. Red Egypt, Thew, Cedar, Warren, 

 and Selection No. 4 of TripolaXTardent Blue. Of 5 varieties of wheat sent 

 from Utah, all w-ere rusted. Two Swedish wheats immune to yellow rust 

 ( Puccinia glumarum) in their native soil were also rusted. 



In tests on the resistance, of different varieties of wheat to smut (TiUctia 

 la-vis and T. tritici), 2 varieties were found to l)e highly smut resistant, viz, 

 Ohio and Genoa. 



The relative efficiency of several fungicides on bunt was also tested. Fun- 

 gusine, a trade compound, showed 81 per cent of the grain germinated and 19.2 

 per cent smutted; copper sulphate, 73 per cent germinated and 2.2 per cent 

 smutted ; formalin, 68 per cent germinated and 8.2 per cent smutted ; 2 per cent 

 solution of phenol, 71 per cent germinated and 16.3 per cent smutted; and the 

 check plat. 85 per cent germinated and 88 per cent smutted. 



The relative effects of copper sulphate and formalin on germination, infec- 

 tion, and yield were also tested. 



Experiments with flag smut designed to test the relative virulence of the dis- 

 ease when smutty seed was sown in clean ground and when clean seed was sown 

 in ground containing diseased straw from previous crops were made, and the 

 effects of different treatments on the seed both before and after Infection were 

 also tried. Smutty seed in clean ground gave 83 per cent of infection and clean 

 seed in infected ground r)2 per cent. Seed dusted with si)ores aTul afterwards 

 treated with coiiper sulphate solution gave no smut, likewise seed first treated 

 with copper suljthate and then dusted with spores. Grain treated with copper 

 sulphate and diseased straw added showed an infection of 2!) |)er cent, and 

 when treated with corrosive sublimate and planted with diseascnl straw an 

 infection of 44 per cent was found. 



Copper sulphate i.s. therefore, only en\'ctive against snmtty seed in a clean 

 soil. Neither copper sulphate nor corrosive sublimate will prevent smutting in 

 soil alreadv contaminated by diseased straw. 



