54 



BOTANICAL GAZETTE [january 



by submerging them in water. Although increased catalase 

 activity generally accompanied intense respiration, this relation- 

 ship did not always hold, for when seeds were submerged a long 

 time the catalase activity slowly increased, but there was no increase 

 of respiration intensity. An examination of tables IX and XVII 

 will show that the catalase gain was proportionally very much 

 larger than the respiration gain during after-ripening. It will also 

 be noted that the catalase gain was greatest at 5 C, where the 

 respiration was low. It is evident, therefore, that there may be 

 increased catalase activity without an increase of respiration. 



TABLE XX 



Catalase activity of after-ripened and desiccated seeds, 

 no. 30 (calculated dry weight 0.0696) 



Rate and percentage of germination. — Juniper seeds 

 germinate most readily at the low temperature of 5 C. These 

 seeds germinate, although very slowly, at o±i°C. They also 

 germinate at io° C. Seeds after-ripened at 5 C. and then placed 

 at io° C. germinated slower than those left at 5 C. After-ripened 

 seeds were thrown into a state of secondary dormancy by exposure 

 to temperatures above 12 C. Their catalase activity gradually 

 decreased and germination ceased. After being thrown into 

 secondary dormancy, several weeks at 5 C. were required to 

 after-ripen the seeds again. The seeds which sank in water gave 

 between 75 and 80 per cent germination at 5 C. 



Growth of seedling. — Table XXI gives the rate and extent 

 of growth for seedlings exposed to the light or the dark at different 

 temperatures. All seeds were germinated at 5 C. and then trans- 

 ferred to the different temperatures. The length of the extending 

 hypocotyl at the time of transfer was 0-1 mm. The seedlings 

 grew the longest and fastest at 25 C. At 30 C. they never attained 



