3o6 BOTANICAL GAZETTE [april 



As after-ripening progresses the hydrogen ion concentration 

 increases, as do also the water holding capacity and the oxidase and 

 catalase activities. 



The greatest amount of free acid is present in the germinating 

 seeds. Autodigestion of pulverized seeds shows the greatest acid 

 increase in the after-ripened ungerminated seeds. This is probably 

 due to their high lipase activity. 



Sambucus. — As high as 77 per cent of germination was obtained 

 by layering fresh seeds out of doors over winter. 



No satisfactory forcing agent has yet been found. A slight 

 forcing effect of several acids, bases, and salts has been observed. 

 The best of these forcing agents are nitrates and sulphates. 



Although Sambucus seeds are probably injured by drying, that 

 is not the only factor to be considered, since freshly gathered seeds 

 with a moisture content of 22 per cent will not germinate when 

 placed on a moist substratum. 



As yet it has been impossible to approximate perfect germina- 

 tion, and much still remains to be learned concerning the conditions 

 necessary to reach it. 



RuBUS. — Dormancy is probably due to the high breaking 

 strength of the endocarp. Seeds treated with concentrated sul- 

 phuric acid for 2 hours, then thoroughly washed, germinate readily 

 on cotton, filter paper, or quartz sand. 



The optimum temperature for germination lies between 20° and 

 25° C. Seeds germinate equally well in light or darkness. Naked 

 seeds germinate poorly in soil. This may be due to the action of 

 fungi, bacteria, or to other causes as yet unknown. 



As a practical method for the germination of Ruhus seeds, if one 

 is not to resort to layering, the writer suggests the following: The 

 seeds should be removed from the pulp as completely as possible. 

 If the berries are crushed and then thrown into water most of the 

 pulp can be floated off. The pulp still clinging to the seeds may be 

 removed by allowing fermentation in water to take place or by 

 treating the seeds with a 5 per cent solution of sodium hydroxide for 

 15-20 minutes, after which they should be thoroughly washed in 

 running water. It is essential to dry the seeds for at least 24 hours, 

 or the treatment with concentrated sulphuric acid which follows 



