[Vol. C 



162 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



periments thus designated. All seed not disinfected will ex- 

 hibit contamination on agar. On the other hand, elaborate 

 experiments might have been made to determine the effect of 

 the disinfectant upon the seed, and in a certain sense these 

 would serve as controls. Our object, however, has been simply 

 to use seed which under the usual conditions of the germinator 

 exhibit a high percentage of germination, so we have merely 

 assured ourselves of the capacity of the seed employed to ger- 

 minate satisfactorily. It is admitted that germination in a 

 Petri dish on agar is not comparable to germination in a ger- 

 minator. 



Experimental Data and Discussion 



At the outset it should be definitely acknowledged that as a 

 general principle the practically perfect disinfection of seed 

 by chemical agents is only possible when the contaminating 

 organisms of the seed are superficial, or largely superficial. 

 This conclusion is drawn from a variety of observations and 

 experiments, the general result of which is too obvious to re- 

 quire elaborate data and discussion but merits mention in re- 

 spect to some pronounced instances. Experiments have been 

 made with seed suspected of more than superficial contamina- 

 tion in the case of corn, sunflower, squash, tomato, and MelUo- 



tus. In the first case, corn of the 1917 crop was obtained in 

 wilich a discoloration of the micropylar end of the seed was 

 characteristic. The normal maturity of this crop in the Mid- 

 dle West was more or less affected by early frost, and in some 

 sections subsequent wet weather induced visible mouldiness. 

 The seed used exhibited no macroscopically visible infection 

 of the cob, but such infection was inferred. After treatment 

 with various disinfecting agents the majority 

 and anv contaminating organisms were either 



of these seed 

 killed by the 



agent, or, in the agar cultures, there was a growth of fungous 

 hyphae from the discolored micropylar end. Such seed were 

 necessarily discarded. The other seed mentioned had been 

 stored under moist conditions, favoring the development of 

 moulds and bacteria, and in no case was it possible to disin- 

 fect any reasonable percentage without iniurv in resr>cct to 



