i 9 2i] PACK—JUNIPERUS 33 



As it has been impossible to dispense with this rest period in all 

 cases, many substances have been used to reduce dormancy and 

 force seeds to germinate. Concentrated sulphuric acid has been 

 used by Hiltner and Kinzel (17), Rostrup (32), and others with 

 positive results. Among the salts Rose (31) noted that the sul- 

 phates and nitrates were the better forcing agents. Hydrogen 

 peroxide and increased oxygen pressure forced the germination of 

 Xanthium seeds (5). Wounding and treatment with ether stimu- 

 lated the germination process (3) . Light has been found to force or to 

 inhibit germination depending on the seed (12, 20) . The New York 

 Experiment Station (24) and many others have shown that desic- 

 cation improves the germinating power of corn. The hot bath 

 has been used with success on some seeds (4). Alternating tem- 

 peratures have been used to force grass seeds in the Seed- testing 

 Laboratories of the Bureau of Plant Industry. With these much 

 has been claimed for freezing and thawing as a forcing agent (29). 

 Lakon (21), however, found that the germination of Pimis Peuce, 

 P. Cembra, P. Strobus, and P. silvestris could not be accelerated 

 by treatment with dry heat, warm bath, file injury, ether, chloro- 

 form, salt solutions, concentrated sulphuric, or dilute acids. 



Seeds with dormant embryos must go through a series of changes 

 (after-ripening) before germination can occur (5). The after- 

 ripening of hawthorn seeds proceeds fastest at 5-6 C. according to 

 Davis and Rose (8). An idea of this after-ripening process may 

 be gained by following the results of Lakon on a protein and 

 Eckerson (10) on a fatty seed. Lakon (22), in studying the 

 changes that precede germination of Fraxinus excelsior, found 

 very little increase in water absorption. From the tenth day on, 

 starch accumulated in the embryo cells, with a corresponding dis- 

 appearance of protein from the endosperm cells. In place of the 

 disappearing protein a turbid emulsion formed, which later was 

 digested. At no time did starch appear in these endosperm cells. 

 The embryo doubled its length during this process of " Vorkeimung." 

 Eckerson (10) studied the changes occurring in the hawthorn 

 seed during after-ripening, and reported an increasing acidity 

 and water absorbing power of the dormant organ. The catalase, 

 peroxidase, and oxidase activity increased as after-ripening and 



