88 



PKINCIPLES OF AMERICAN FORESTRY. 



freezing, while others require a much higher temperature. 

 (6) After seeds of some plants have become very dry, 

 scalding may aid them in germinating, while with others, 

 scalding is injurious. It is sometimes desirable to soak 

 seeds for one or two days in tepid water and then mix 

 with sand and freeze before sowing. Lindley records 

 that seeds found in raspberry jam grew after passing 

 through the heat necessary to boil syrup (240 degrees 

 Fahr.), and that seeds of Acacia grew after being boiled 

 five minutes, but our common tree seeds will not stand 

 such treatment. 



Amp,' 



Fig. 20. — Cross-section of stratifying pit for storing seeds during 

 winter, covered with inverted sods. 



Stratification, as the term is used in this connection, 

 refers to the storing of seeds mixed with layers of earth, 

 leaves, or other material. It is customary to apply the 

 term solely to seeds that are mixed in this way and kept 

 frozen over winter. It is the common practice with the 

 seeds of such trees as the Black Walnut, Hickory, Bass- 

 wood, Plum, Cherry, and Mountain Ash. Where only 

 small quantities are to be cared for they are generally 

 mixed in boxes and the boxes buried in well-drained soil 



