1919] 



DUGGAR AND DAVIS — SEED DISINFECTION 161 



has been invariably carried out in a transfer room repeatedly 

 steamed to insure the precipitation and fixation of dust parti- 

 cles. In some cases the seed were preliminarily immersed in 

 running water for from 4 to 16 hours, in other cases dry seed 



were treated directly. 



In the earlier work the selected seed w T ere placed in small 

 cheese-cloth bags, and these immersed in covered vessels con- 

 taining the disinfecting solutions employed. After the inter- 

 val of treatment the bags were transferred to jars of sterile 

 distilled water for from 15 minutes to 1 hour, and when it 

 seemed desirable a second quick rinsing was given. The con- 

 tents of each bag was then carefully dumped into a sterile 

 Petri dish. In later work the washed or soaked seed were 

 carefully placed in sterile Erlenmeyer flasks, and the disin- 

 fectant then poured in, a separate flask being used for each 

 lot of seed to be treated for any interval of time as well as 

 each concentration of disinfecting solution. After treat- 

 ment the seed were twice shaken with sterile water, the second 

 wash water remaining not less than 15 minutes. The seed 

 were then transferred to a Petri dish by means of a metal 

 spoon. All implements employed were sterilized by dipping 

 in alcohol and then promptly burning this off. 



The purity and germination of the seed were then followed 

 after their transfer to large Petri dishes containing standard 

 potato decoction agar. Care was taken to insure intimate con- 

 tact of the seed with the medium. From 15 to 50 seed, de- 

 pending upon size, were usually arranged in each dish, and 



each test duplicated. 



Inasmuch as the essential thing in such work is to obtain a 

 high percentage of germinating seed free from contamination 

 and readily transferable to other cultures, the above methods 

 have seemed entirely adequate, and complicated apparatus, 

 such as that devised by de Zeeuw 1 , is not merely unnecessary, 

 but it is in general impracticable. 



In the true sense of the word ' ' control ' ' experiments are not 

 possible in this work, and no attempt is made to include ex- 



l Zeeuw, R. de. The comparative viability of seeds, fungi and bacteria when 

 subjected to various chemical agents. Centralbl. f. Bakt. II. 31 : 4-23. 1 f. 1911. 



