conspectus: methods of control 71 



kernels and retards germination of the rest. The whole sub- 

 ject of germicidal treatment needs careful revision. 



Since the above was written Harry Braun of my laboratory 

 has discovered (1919) that injury to seed-wheat, which is 

 considerable when formalin solutions or copper sulphate solu- 

 tions are used, is eliminated by soaking the seed in water for 

 10 minutes and then keeping it moist for 6 hours before 

 treating it. This allows it to absorb sufficient water to become 

 resistant, since most of the injury is caused by the for- 

 maldehyd that is carried into the grain along with the imbibition 

 water. It is then soaked in one part of formalin to 400 parts 

 of water for 10 minutes, drained, and covered for six hours to get 

 effective action of the remaining aldehyd vapor on all the 

 parasites, whereupon it is dried and planted. His work, re- 

 peated many times on different varieties of wheat and to some 

 extent also on other grains, shows nearly as full germination 

 and quite as good growth in the treated plots as in the control 

 plots. In fact, growth from the treated seeds is stimulated a 

 little (Fig. 51). 



In studying pear blight Reimer found (1918) that 1 part 

 of formalin in 9 parts of water is very effective for destroying 

 the Bacillus amylovorus both on tools and in the tree wounds. 

 He also found I500 cyanide of mercury in water destroyed the 

 pear blight organism in tree wounds effectively (with some slight 

 injury to the wound) while Bordeaux paste or I500 mercuric 

 chlorid water often failed. His Ho 00 cyanid of mercury 

 water was not always effective, and he still has formalin treat- 

 ment and the proper dose of cyanid under consideration 

 (see Part III, No. XII). The cyanides, it should be remem- 

 bered, are deadly poisons to man and the domestic animals. 



A. Check. Each kernel is surrounded by a pure culture of the yellow slime. 



B. Treated seeds. All are free from bacteria. The seeds were first baked to 

 kill surface saprophytes, then soaked in a thick bouillon suspension of the black- 

 chaff organism made from a young agar culture. Dried a day or two, exposed to 

 the formalin and then planted on the nutrient agar. 



Nine active isolations of the black-chaff organism were tested in this series. 

 Of the 894 formalin treated seeds only 13 showed any growth of the black-chaff 

 organism after 8 days on the nutrient agar. Of the 528 check seeds all but 5 

 developed colonies of the black-chaff bacterium. Photographed December 4, 1918. 



