PERIODICAL LITER,\TURE 485 



seeds were sterilized after heating. The germinating dishes were also 

 sterilized and care used in planting. By this practice the germinating 

 seeds were kept free from fungal growth for several weeks. 



The results of the author's studies on seeds heated at variable 

 lengths of time at 87.5 degrees C. show that there is a gradual decrease 

 in the percentage of germination with increased time of heating. Also 

 after the delayed seeds germinated their growth was much slower 

 than that of unheated seeds. The effects produced by heating were 

 similar to those produced by the storage of se'eds at room temperature, 

 thus indicating a similar change in the seed in both cases. 



In these studies the author selected the time required to kill 75 

 per cent of the seed at the end point. It was found that there is a 

 definite relation between temperature and the time of exposure neces- 

 sary for killing 75 per cent of the seed. By determining the time 

 required to kill seeds at any two definite temperatures, the time re- 

 quired for killing seeds at any other temperature was calculated from 

 Lepeschkin's formula, T = a — b log Z, in which Z is the time in 

 minutes and a and b are constants. 



The author states that if the loss of viability of seeds during 

 storage is a matter of the coagulation of cell proteins of the embryo, 

 this time-temperature formula for the coagulation of proteins should 

 be applicable as a temperature-life duration formula for seeds. 



A rather close agreement was found between calculated values by 

 means of Lepeschkin's formula and those found by experiment, thus 

 indicating that the time-temperature formula for the coagulation of 

 protein can be applied as a temperature-life duration formula for seeds. 



The article throws light on the nature of the processes in the loss 

 of viability of seeds in storage and suggests the possibility of the 

 quantitative measurement of various storage conditions and their 

 significance, especially moisture and temperature, upon the longevity 

 of seeds. J. W. T. 



Botanical Gazette, March, 1917, pp. 169-89. 



An interesting account is given by Illick of 



American Species the introduction of American tree species into 



in Germany, from which it appears that as early 



Germany as 1566 the eastern arborvitae was introduced 



and during the seventeenth century, black locust, 



bald cypress, tulip tree, red cedar, and balsain tir, found their way 



