58 BOTANICAL GAZETTE [january 



seed, but these changes, as has been outlined, are quite different 

 from those occurring during after-ripening. Seeds ready to 

 germinate (after the coat is cracked and their water content 

 increased to 52 per cent) are killed by an exposure to — 5 C. 



6. The juniper seed has a dormant embryo that must after- 

 ripen before germination. After-ripening occurs at temperatures 

 between 0=1= i° C. and io° C, although fastest at about 5 C. 



7. The changes that accompany after-ripening of the juniper 

 seed at 5 C. were found to be as follows: (1) rather rapid and com- 

 plete imbibition, followed by a steady slow decrease in water con- 

 tent during after-ripening or until near germination; (2) increased 

 H + ion concentration, especially of the embryo; (3) an increment 

 of titratable acid ; (4) a steady and enormous increase in the degree 

 of dispersion of the stored fat; (5) decrease in the amount of stored 

 fat and protein, with an increase of sugar content and the first 

 appearance of starch; (6) the translocation of food in the form of 

 fat or fatty acids from endosperm to embryo; (7) a seven-fold 

 increase in the amino acid content, and a complete disappearance 

 of histidine from the endosperm; (8) an increase of soluble proteins 

 with a marked hydrolysis of the stored proteins: (9) slight growth 

 of embryo; (10) very slight increase of the respiration intensity; 

 (n) increased respiratory quotient; (12) decreased intramolecular 

 respiration; (13) a doubling of the catalase activity ; and (14) the 

 rise in vigor of seeds as shown by their resistance to fungal attack* 



8. In conjunction with after-ripening at 5 C, desiccation seems 

 to be the only promising means of shortening this after-ripening 

 period. 



9. The time at which the hypocotyl breaks through the nucel- 

 lus was fixed as the end of after-ripening and the beginning of 

 germination. 



10. Neither the resting nor the after-ripened juniper seeds 

 yield more than about 1 per cent germination at temperatures 

 above 15 C. Seeds after-ripened at 5 C, then placed at io° C, 

 germinate slower than those left at 5 C. When after-ripened 

 seeds are transferred from 5 C. to temperatures above 15 C. they 

 are thrown into a state of secondary dormancy. Hence these 

 seeds require a low temperature for germination as well as for 

 after-ripening, and therefore no seed should be transferred to 



