juiyis, i9-'o Presoak Method of Seed Treatment 391 



research, result in a saving of a large percentage of seeds destroyed by 

 the usual treatments or delayed in germination and thus longer exposed 

 to the attack of soil fungi, giving at the same time a more efficient germi- 

 cidal action on the pathogens involved. 



SUMMARY 

 (i) The use of formalin and copper sulphate as now practiced usually 

 causes retardation and injury to seed germination. 



(2) Greenhouse and field experiments here reported have shown that 

 this detrimental effect can be eliminated for standard varieties of wheat 

 by allowing the seeds to absorb water for six hours before submitting 

 them to the treatment with formalin or copper sulphate. Soaking for a 

 short period (10 minutes) and covering for 6 hours, here designated the 

 presoak method, is better than leaving in water for 6 hours. Similar 

 results were obtained in experiments with barley, oats, and com. 



(3) The saturation of the seed cells and cell walls with water during 

 the presoak period appears to be the factor counteracting the injurious 

 efifect on seed germination by diluting the disinfectant beyond the point 

 of injury as it diffuses into the tissues and also by considerably decreas- 

 ing the amount of water plus disinfectant solution which may enter the 

 tissues after presoaking as compared to what may enter without any 

 presoaking. 



(4) Actual stimulation of germination has been observed repeatedly in 

 presoak-treated seeds, a factor wliich by shortening germination min- 

 imizes the danger of exposure to the attack of soil organisms during this 

 susceptible period. 



(5) The bacterial blackchaff disease of wheat can be controlled with- 

 out any injury to seed germination by a 6-hour presoak of surface- 

 infected seeds in water followed by a 6-hour treatment with formahn i 

 to 400 in the manner prescribed. 



(6) In practice, wheat seeds after being screened should be soaked 

 with water for 10 minutes at about 6 o'clock in the morning, drained, 

 covered, and set away moist till noon, then soaked with formalin i to 

 400 for 10 minutes, drained, covered, and set away moist till 6 o'clock in 

 the evening, when they should be spread out to dry overnight to be 

 ready for planting the next day. 



(7) In planting, an allowance must always be made for the fact that 

 ' there are fewer treated seeds in a bushel than there are of dry untreated 



ones. In general, it is recommended to sow about 25 per cent more bulk 

 than is usual of the dry grain, otherwise fewer seeds will be actually 

 planted and the yield will be reduced correspondingly. 



(8) The use of the presoak method tends to increase the efficiency of 

 the disinfectant, in that the presoaking stimulates dormant bacteria and 

 possibly fungi into vegetative activity, thereby rendering them extremely 

 susceptible to the subsequent action of the disinfectant. 



(9) The general use of the presoak method of treatment in farm 

 practice for other diseases involves no radical change in present procedure, 



