76 



so, the roots would soon be surrounded 

 with such substances, and would be in- 

 capable of absorbing nutriment. In chalk 

 districts eternal woods are found composed 

 of nothing but beech ; in other soils, of 

 nothing but oak. The oldest vineyards 

 and the oldest hop-gardens are the best. 

 (I say nothing of old meadows, since trees 

 are in question.) In all these cases, if 

 the roots excreted substances unfit for 

 nourishing the plants the whole soil 

 would have become saturated with them. 

 Land plants grown in water are always 

 unhealthv. Under these circumstances, 

 may not colouring matter, or other sub- 

 stances supposed to be excretion, be the 

 result of disease and decay or partial 

 maceration of the roots. There is no 

 discoloration of the water in which the 

 seedlings of forest trees al^e made to grow. 



I imagine that the roots of trees, in 

 absorbing the moisture with which they 

 come in contact, give off the unnecessary 



