42 BOTANICAL GAZETTE [january 



fourth and sixth month the germination reached 10 per cent, a 

 very marked increase over that obtained at the higher tempera- 

 tures. When the temperature of the water rose much above 12 C. 

 germination ceased. These results show that the increased germina- 

 tion was not due to the removal of inhibiting substances from the 

 coat, but to the effect of the low constant temperature. 



Although many observers (11, 20, 29, 30) have reported a for- 

 cing action for freezing and freezing with thawing, these results show 

 that when freezing really occurs it is very injurious. On March 14, 

 1919, 1000 air-dry seeds and 1000 moist seeds were placed at a 

 constant temperature of - 23 C; and 1000 air-dry and 1000 moist 

 seeds were subjected to an alternation of temperature between 



- 23 and io° C. The latter seeds were left at each temperature 

 for one week. After 45, 95, and 150 days of exposure samples 

 were removed for study. The catalase activity of these seeds for 

 45 and 95 days is given in table IX. The catalase activity of seeds 

 stored dry at — 23 C. equaled that of untreated seeds, while that 

 of seeds stored wet at - 23 C. and wet or dry at the alternating 

 temperature showed a marked decrease. There was no change in 

 the oxidase or peroxidase activity. The seeds stored dry at 



— 23 C. showed no increase of H + ion or titratable acid over that 

 of the untreated seed. All other seeds showed a slight increase of 

 sugar content and of H + ion concentration; also a 40 per cent gain 

 of titratable acid. Both embryo and endosperm of these seeds, 

 stored at the alternating temperatures, had the same H + ion con- 

 centration. The fats in these seeds were very soluble, not charac- 

 teristic, and diffused throughout the endosperm and embryo. 

 This general diffusion of the fats and the equal H+ ion concentration 

 for the embryo and endosperm indicate that the membranes had 

 become more permeable by freezing (16). On staining these seeds 

 with methylene blue they appeared to be dead. Samples of all 

 seeds were put under favorable conditions for after-ripening and 

 germination, but only the seeds that were stored dry at - 23 C. 

 after-ripened and germinated. These results prove that these low 

 temperatures are very injurious unless the seeds are dry. It is 

 probable that seeds stored at this low constant temperature and 

 protected from moisture would retain their viability many years. 



