G4 SYLVA AMERICANA. 



Achard, were afterwards repeated and confirmed by a number 

 of other modern chemists, who found that seeds will not germinate 

 in nitrogen gas, but will die if put into it even after germination, 

 at least if the radicle only is developed. Senebier found that 

 seeds will not germinate in an artificial atmosphere that does not 

 contain at least one eighth part of its bulk of oxygen ; but that 

 the most favorable proportion is when it contains one fourth part. 

 It has been ascertained, however, that seeds will germinate even 

 in an atmosphere of pure oxygen, though not so readily as when 

 presented in a state of mixture or combination with other gasses. 

 It cannot indeed be necessary that the oxygen consumed in 

 germination should be presented to the seed in an uncombined 

 state ; as is obvious from the natural agency of the atmospheric 

 air, as well as from direct experiment. Humboldt found that 

 the process of germination is accelerated by means of previously 

 steeping the seed in water impregnated with oxymuriatic acid. 

 In all cases of germination the presence of oxygen is necessary. 

 For even of those seeds that germinate in water, the germination 

 takes place only in consequence of the oxygen which the water 

 contains in an uncombined state. The period necessary to 

 complete the process of germination is not the same in all seeds, 

 even when all the necessary conditions have been furnished. 

 Some, species require a shorter, and others a longer period. 

 The grasses are among the number of those plants whose seeds 

 are of the most rapid germination ; then perhaps cruciform plants ; 

 then leguminous plants ; then labiate plants ; then umbelliferous 

 plants ; and in the last order rosaceous plants, whose seeds 

 germinate the slowest. The following table indicates the periods 

 of the germination of a considerable variety of seeds as observed 

 by Adanson. 



Wheat, millet seed, . . 1 



Spinage, beans, mustard, . 3 



Lettuce, anise seed, . . 4 



Melon, cucumber, cress seed, 5 



Radish, beet root, ... 6 



Barley, 7 



Orach, 8 



Days. Days. 



Purslain, 9 



Cabbage, 10 



Hyssop, 30 



Parsley, . . . . 40 or 50 

 Almond, chesnut, peach, 1 year. 

 Rose, hawthorn, filbert, 2 years. 



