36 GERMINATION. 



day ; and observation has taught us, that in some instan- 

 ces, it proceeds most rapidly in the dark. 



The following table will serve to shew how various 

 are the periods requisite for the germination of differ- 

 ent seeds, some requiring a greater degree of heat, and 

 some more moisture than others, and some also requir- 

 ing a longer exposure to all the exciting causes of ger- 

 mination. 



days days 



Wheat and Millet require 1 Purslain 9 



Spinage, Beans, Mustard 3 Cabbage 10 



Lettuce, Anise 4 Hyssop 30 



Melon, Cucumber, Cress seed 5 Parsley, 40 or 50 



Radish, Beet 6 Almond, Chesnut,* Peach 1 year 



Barley 7 Rose, Hawthorn, Filbert 2y'rs 

 Orach 8 



No seeds vegetate so rapidly as those of the grasses, 

 and none require a longer period than those of the Rose 

 and others of the same natural order. 



But from what has previously been said, we must 

 expect to see a variation of these periods in conse- 

 quence of the more or less favourable situations in 

 which the seeds are planted. 



Philosophers have in vain attempted to determine 

 why plants invariably assume an erect position, why as 

 the rostel descends towards the centre of the earth, 

 the plumelet always rises above its surface. Art may 

 force a young shrub to the horizon but its branches will 

 still ascend as if they spurned a contact with the earth 

 which supports them ; and if a germinating seed be 

 made very gradually to revolve, the spiral form of its 

 rostel will show that it has uniformly aimed to descend. 

 Delahire supposed that plants become erect in conse- 

 quence of the volatile nature of their fluids, the expla- 

 nation of Mr. Knight rests upon mechanical principles, 



