LIFE SPAN OF SEEDS 



49 



Figure 15. Embryos of lower seed of cocklebur. A, Imbibed embryo of non-dormant 

 seed; B, same 14 days after planting; C, same 21 days after planting. D, Embryo of 

 dormant seeds after 18 days in germinator; E, same as D after 18 days in germinator, 

 plus 14 days in soil, or 32 days in germinating conditions; F, same after 18 days in 

 germinator, plus 29 days in soil, or 47 days in germinating conditions. 



follo^^^ng mnter? In any case, Davis has thrown much hght upon the 

 dormancy and after-ripening rhythm of seeds in nature. 



Hard Seeds Best Adapted for Long Life Span 



We have been discussing the Hfe span of soft seeds (seeds that absorb 

 water) in the soil and find that some of them stay aUve for 60 years or 



