Aug. 14. 19 16 



Agricultural Value of Impermeable Seeds 



767 



creased the rate at which they softened. As will be shown later, how- 

 ever (p. 775), moderate heating of thoroughly air-dried seeds of these 

 plants has little or no effect under ordinary conditions. 



MONTHS *H0 r£*PS 



Fig. i .-Curves showing the rate of softening of impermeable red-clover seeds of different degrees of maturity. 

 ESTIMATION OF THE GERMINABILITY OF IMPERMEABLE SEEDS 



It is evident from the preceding discussion that it is impossible to 

 estimate in advance what proportion of the impermeable seeds of a 

 given lot will germinate under ordinary germination conditions in any 

 given length of time. At one time Nobbe (14) proposed that one-third 



