192 1] PACK—JUNIPERUS 39 



Methods. — As it has been shown that catalase activity increases 

 with after-ripening of the dormant-embryo seeds (6, 10), catalase 

 activity was chosen as the first standard. Germination, the produc- 

 tion of independent seedlings, was selected as the final standard. 

 Great care was found necessary in the preparation of material and 

 the manipulation of the catalase apparatus. As the berry has a 

 high catalase activity, every trace of fruit was removed before 

 grinding. The grinding was carried out under similar conditions, 

 and with a definite amount of water and no. 2 sand per unit weight 

 of seed material. The dioxogen was neutralized with N/10 NaOH 

 at the time of using. All determinations were made with the 

 bath at 25° C., and the drive wheel of the apparatus regulated to 

 make 30 revolutions per 10 seconds. No explanation is needed for 

 germination as a standard. 



Forcing agents.- — Among the common forcing agents tried on 

 the juniper seeds were high temperatures, alternating tempera- 

 tures, removal of coats, hydrogen peroxide, dilute acids, carbon 

 dioxide, light, soil, mercuric chloride, ether, and oxygen. The 

 first seven of these had very little effect on the catalase activity 

 and did not force germination. While the treatments with mercuric 

 chloride, ether, and oxygen did not force germination, each had its 

 influence upon catalase activity. 



Crocker and Harrington, in an unpublished work at the Seed- 

 testing Laboratories of the Bureau of Plant Industry, have found 

 that HgCl 2 was a good forcing agent for Johnson grass. Juniper 

 seeds were sterilized and put into flasks containing the following 

 concentrations of HgCl 2 . After 24 hours the excess of liquid was 

 poured off. The results are given in table V. These data, as 

 well as those obtained by grinding the seeds for catalase activity 

 in the same concentrations, show that HgCl 2 reduced catalase 

 activity in the higher concentrations. None of the seeds treated 

 with HgCl 2 germinated. 



In studying the effect of ether, seeds were sterilized, put into 

 Petri dishes without covers, and exposed to air containing various 

 amounts of ether by sealing in 9 liter cans. After a certain exposure 

 the seeds were removed, aired, and placed to germinate. Table VI 

 gives the catalase activity for seeds that were exposed to ether 



