14 



ROOT. 



purpose of multiplication ; as those of Cydonia 

 Japonica, &c. 



The cause of this power existing in some 

 species, and not in others, is unknown. 



It is therefore a power that can never be 

 calculated upon ; and whose existence is only 

 to be discovered by accident. 



The immediate cause of the formation of 

 roots is at present involved in obscurity, but the 

 fact is well known that some plants when pro- 

 pagating by cuttings produce roots with much 

 more facility and in a shorter time than others. 



Darkness, moisture, and perfect rest, seem 

 necessary for this purpose — as well as a down- 

 ward circulation of the sap, which is effected 

 by the action of the leaves on the upper part 

 of the stem — nor can the roots exist by them- 

 selves without the leaves to create the action 

 of drawing up the juices they absorb — therefore 

 a cutting without leaves will soon perish. 



Although roots are generated under gound, 

 and sometimes at considerable depths, yet ac- 

 cess to a certain quantity of atmospheric air 

 appears indispensable to the healthy execution 

 of their functions. This is constantly exem- 

 pUfied in plants growing in the earth at the back 

 of an ill-ventilated forcing house, where the 



