94 FROCESt OP VEGETATION-. 



f rmer the young plants rose to the height 

 of two inches, or more, in a week's time ; in 

 the other none appeared, till after the pot 

 had been removed for a similar period into 

 the air again. Seeds buried in the ground 

 to a greater depth than is natural to them 

 do not vegetate, but they often retain their 

 power of vegetation for an unlimited period. 

 Earth taken from a considerable depth will, 

 when exposed to the air, be soon covered with 

 young plants, especially of Thistles, or of the 

 Cress or Mustard kind, though no seeds have 

 been allowed to have access to it. If the 

 ground in old estabhshed botanic gardens be 

 dug much deeper than ordinary, it frequently 

 happens that species which have been long 

 lost are recovered, from their seeds being 

 latent in the soil, as I have been assured by 

 Mr. Fairbairn of Chelsea garden, and others. 

 The integuments of the seed, having ful- 

 filled their destined office of protection, burst 

 and decay. The young root is the first part 

 of the infant plant that comes forth, and by 

 an unerrino; law of Nature it is sent down- 

 wards, to seek out nourishment as well as to 

 fix the plant to the ground. In sea-weed s» 



