12 MASS. EXPERIMENT STATION BULLETIN 213. 



Some of the growers, however, reported that they injured the seed by 

 the corrosive subhmate treatment. Some said that germination was 

 retarded, others that the percentage of germination was lowered; and 

 others that the seed would not germinate at all. It was at first thought 

 that the failure was due to faulty technique, but laboratory tests showed 

 that even a treatment of thirty minutes was not harmful, and some of the 

 growers omitted the washing of the seed after sterilizing without any 

 bad effect. Some reported lack of germination in seed which was sterilized 

 at the tobacco substation by Chapman. It was certain, then, that the 

 injury could not be attributed to faulty technique in all cases. Inquiry 

 among the growers as to the method by which they sprout the seed revealed 

 one difference between their method and that used at the stations, viz., 

 the custom which many growers have of cracking or sproutmg the seed 

 in moist cocoanut fiber or apple punk or between sods for a few days before 

 planting. The seed is kept in a warm room of 70 to 90° F. and from time 

 to time sufficient water is added to keep the fiber or other material slightly 

 moist. It was thought that possibly the fiber might have something to 

 do with the lack of germination and some of the seed was taken to the 

 laboratory for test, using both unsterilized and sterilized seed of different 

 lots. It was found that the unsterilized seed sprouted in the fiber and that 

 the sterilized seed did not show any signs of sprouting even after ten 

 days. Other growers brought in samples of seed which they themselves 

 had sterilized and which had failed to sprout in fiber, and these lots were 

 tested also. Chapman tried varying the conditions under which the seed 

 was kept during the sprouting period and found that under the condi- 

 tions ordinarilj^ used it was almost impossible to sprout the sterilized seed, 

 although the same seed in Petri dishes would germinate satisfactorily. 

 It was found finally that in order to germinate sterilized seed, whether 

 in punk or fiber, the pans should be kept at a lower temperature and also 

 that the moisture content of fiber or punk must be considerably higher 

 than usual. By close attention to these factors it was possible to sprout 

 the different lots of sterilized seed in either punk or fiber almost as well 

 as before sterilization. 



Lack of germination of sterilized seed under usual conditions in punk or 

 fiber appears to be due to the fact that the seed coat is hardened by the 

 washing and drying and there is a much slower softening of the seed coat 

 than is the case with the unsterilized seed. This was tested in the follow- 

 ing way: — 



Experiment 7. — Of two lots of seed, one was sterilized for fifteen minutes with 

 a solution of Wooo corrosive sublimate, and the other treated for fifteen minutea 

 in pure water without any chemical added. Both lots were taken from the jars 

 and washed and dried in the usual manner. It was found to our surprise that both 

 lots reacted the same; i.e., when placed in punk or fiber under normal conditions, 

 the germination was greatly delayed or lacking. Tins experiment showed that lack 

 of germination was not due to the corrosive sublimate treatment, but to another 

 cause, probably the hardening of the seed coat by the washing process or possibly 

 by the rapid drsnng. 



