392 Journal of Agricultural Research voi. xix, no. s 



the only deviation being to keep the seeds moist for a definite period 

 before giving them the disinfectant treatment. 



(id) In applying the principles here utilized to other kinds of seeds, 

 the determination of the lengths of the two parts of this method — (i) the 

 presoak period, (2) the subsequent disinfectant treatment period — must 

 be governed by the following factors : (a) the rate of absorption of water 

 by the seeds, (b) the susceptibility of the seeds and pathogens to the 

 disinfectant, and (c) the respective periods necessary for the beginning 

 of seed germination and of vegetative activity of the pathogen. In no 

 case must the presoak period be continued until seed germination begins. 

 The length of time necessary for the seeds to absorb about 30 per cent of 

 their weight of water is suggested as the length of the presoak period 

 when not conflicting with the other factors involved. 



(11) The presoak method of treatment, as here formulated, is pro- 

 posed as a basis for the reinvestigation of practical seed treatment for 

 all seed-transmitted diseases of economic importance amenable to control 

 by formalin and copper sulphate as a means of eliminating seed injury 

 and at the same time increasing germicidal efficiency. 



LITERATURE CITED 

 (i) Braun, Harry. 



I919. PRESOAKING AS A MEANS OF PREVENTING SEED INJURY DUE TO DISINFECT- 

 ANTS AND OF INCREASING GERMICIDAL EFFICIENCY. In Science, n. S. V. 

 49, no. 1275, p. 544-545- 



(2) Heald, F. D. 



1908. SEED TREATMENT FOR THE SMUTS OF WINTER BARLEY. In Neb. Agf. Expt. 



Sta. 2ist. Ann. Rpt. [igoyJ/oS, p. 45-53, illus. 



(3) Humphrey, H. B., and Potter, A. A. 



I918. CEREAL SMUTS AND THE DISINFECTION OF SEED GRAIN. U. S. Dept. AgT. 



Farmers' Bui. 939, 28 p., 16 fig. 



(4) Johnson, A. G., Stakman, E. C, and Potter, Alden A. 



1918. TABULAR COMPILATIONS AND PRELIMINARY REVIEW OF RESULTS ON SEED 



INJURY TESTS WITH STANDARD DISINFECTANTS. Prepared in Off. Cereal 

 Invest. Bur. Plant Indus. U. S. Dept. Agr. for the War Emergency Bd. 

 of Amer. Plant Path. Mimeographed. 



(5) Smith, Erwin F. 



1917. BLACK CHAFF OF WHEAT. In U. S. Dept. Agr. Bur. Plant. Indus. 

 Plant Disesase Survey, Plant Disease Bui. v. i, no. 2, p. 40. 



(6) 



1917. A NEW DISEASE OF WHEAT. In Jour. Agr. Research, v. 10, no. i, p. 51-54, 

 pi. 4-S. 



(7) 



1918. BLACK CHAFF OF WHEAT. In U. S. Dept. Agr. Bur. Plant Indus. 

 Plant Disease Survey, Plant Disease Bui. v. 2, no. 6, p. 98-99. 



(8) JoNES, L. R., and Reddy, C. S. 



1919. THE BLACK CHAFF OF WHEAT. In Science, n. s. v. 50, no. 1280, p. 48. 



(9) Stuart, William. 



19OI. formalin AS A PREVENTATIVE OF OAT SMUT. Ind. Agr. Exp. Sta. Bui. 

 87, 26 p. 



(10) Thomas, C. C. 



1919. SEED DISINFECTION BY FORMALDEHYDE VAPOR. In Jour. Agr. Research, 

 V. 17, no. I, p. 33-39, illus. 



