flERMIXATIOX. ITo 



If seeds are freed of their pericarp, the water 

 absorption no longer remains the same, for under such 

 circumstances the conditions are much changed, and 

 the moisture taken out is very much less, which fact in 

 itself shows the very important role of the outer cover- 

 ing. The differences are still more striking when seeds 

 in their natural condition are compared with those 

 where the pericarp has been partly removed by simple 

 friction between fingers, and finally with those seeds 

 from which the pericarp has been entirely removed. 

 These seeds, after remaining for three days submitted 

 to watery vapor, had increased in weight 23.6 per cent., 

 15.7 per cent, and 11 per cent, respectively. The time 

 needed for seed to absorb water is very much greater 

 with the pericarp than without it ; in the latter case, the 

 total absorption is completed in seven hours, while in 

 the former, at least twenty-four hours are required, 

 from which fact the very important function of the 

 outer covering of the seed is manifest, as the embryo 

 can draw from it its moisture during its early stages 

 of development. 



Light. 



The principal action of light is after the 

 seed leaves have appeared above ground; this will be 

 discussed under another heading; but as regards the 

 direct action of light, it is not as important as one 

 might suppose. True, with some plants the germina- 

 tion of seed has a certain dependence upon light, but 

 experiments with beet seed show beyond cavil that the 

 differences between the effects of germination in the 

 dark or by a strong light are so slight that they need 

 scarcely be considered. Knauer's experiments upon 

 100 seeds in light, after 14 days, gave 268 sprouts, and 

 in complete darkness, 262. The same may be said of 

 various colored lights. The germinating power of 

 beet seed varies very much from year to year. Dr. 



