152 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 6 



tain seeds, but by extensive tests many more might be added 

 to the list. 



Inasmuch as it is not possible to include a test which is in 

 every sense a control, it may be well to state at this point 

 that the germination of all seed was tested out under usual 

 conditions for germination and in every case ranged from 95 

 to 100 per cent. 



The second disinfectant employed was formaldehyde. It 

 is especially toxic to many parasitic fungi inducing plant dis- 

 eases. In practically all cases where it has been unsuccess- 

 fully used as a general germicide, the failure has been due 

 rather to its injurious action upon the seed than to ineffec- 

 tiveness in controlling fungi and bacteria. Seed injury has 

 been especially noticeable where the gas method has been used. 

 If the seed contains a large amount of water, the gas is ab- 

 sorbed more readily and the seed is promptly injured. 



The method employed was the same as the previous one ex- 

 cept that the seeds had to be washed free of the disinfectant. 

 It was found after many trials that one thorough rinsing in 

 sterile water was sufficient to remove enough of the formalde- 

 hyde to prevent the antiseptic action from affecting the germi- 

 nation and development of the seed. The time intervals for 

 removing seed from the solution were usually 15, 30, and 45 

 minutes. The effectiveness of the fungicide is shown in table 

 ii. Formaldehyde was very effective for a large proportion 

 of the seed used. In most cases, better results were obtained 

 when the seeds were left in a stronger solution a shorter time. 

 Excellent results were obtained when the seeds were first 

 dipped momentarily in 70 per cent alcohol, or for a definite 

 preliminary period in hydrogen peroxide. Where the seeds 

 are fairly resistant this method of treatment is the logical 

 one. Only fair results could be obtained with either cotton or 

 potatoes. In the case of the former, the seed had to be de- 

 linted with concentrated H2SO4 and then subjected to the for- 

 maldehyde treatment. In the case of the potato it was diffi- 

 cult to prevent bacterial growth. Eyes with a very small por- 

 tion of the potato (1 c. cm.) were washed for twelve hours, 



