IQ2l] 



PA CK— JUNIPER US 



37 



sterilization were easily and quickly removed. The bad seeds were 

 floated off with water, and the good seeds rinsed and permitted to 

 dry before sterilization. 



After some testing, a 5 per cent solution of formalin acting for 

 2 . 5 minutes was selected as the best sterilizing agent for juniper 

 seeds. It was found that formalin did not readily penetrate the 

 coat, reduce the catalase activity, or hinder germination. The 

 permeability of the coat was studied as follows. Seeds were sub- 

 merged in different solutions for a definite time, removed, washed 

 in distilled water, the coats removed, the seeds sectioned with a 

 freezing microtome, and the sections tested for the respective solu- 

 tions. Table III shows that the coat was very permeable to water, 

 bases, and salts, but not permeable to stains and acids. 



TABLE III 



Permeability of coats to water, stains, acids, bases, formalin, and salts 



That the salts (AgN0 3 and HgCl 2 ) penetrated the coats is 

 shown by the catalase activity of the seeds with coats removed 

 (table IV). These seeds, after being sterilized, washed, and incu- 

 bated at 9 C. for 48 hours, had coats removed, and were ground 

 for catalase activity determinations. It was further shown that 

 AgN0 3 penetrated the coats by the fact that seeds so treated were 

 killed. Seeds sterilized in formalin germinated, and therefore most 

 of the seeds used in these experiments were sterilized 2 . 5 minutes 

 in 5 per cent formalin. In this connection it should be noted that 

 Schroeder (33) and Groves (14) found that the coat of the wheat 

 seed was practically impermeable to AgN0 3 , and that this solution 

 was a good sterilizing agent for wheat. This shows how the per- 

 meability of seed coats may vary with different seeds. 



