LECT. V.J THE ROOT. 197 



if they be bent down and laid under the earth. In- 

 deed it is not absolutely necessary to lay them un- 

 der the ground to produce this effect ; for a ligne- 

 ous plant growing in a sterile soil, provided the 

 situation be shady and the air damp, will throw 

 out roots from its branches, resembling those 

 protruded by Ivy. I have in my possession a por- 

 tion of the branch of a Bay, Laurus Indica, in the 

 whole length on one side of which the bark is rup- 

 tured, owing to the protrusion of numerous short 

 rootlets. The plant from which this branch was 

 cut, was growing (in 1814) in a kind of cave, 

 formed by the intertwining roots of a noble Beech, 

 on the summit of a chalky bank, in Lord Derby's 

 grounds, near Epsom. The chalk had mouldered 

 away from under the roots of the Beech, which, 

 projecting forward as a roof, shaded the Bay that, 

 perhaps, had been originally planted close at the 

 foot of the bank : but all the soil had been long 

 since washed away from its root, which adhering 

 to the bare chalk, served no longer as an ab- 

 sorbing organ, but merely to sustain the plant in 

 its upright , position ; and as there were very few 

 leaves on the branches, the rootlets, which were 

 protruded from them, evidently maintained the 

 life of the plant, by absorbing the water held in 

 solution in the air of the shady spot where it grew. 

 On the knowledge of facts such as these, plants 

 are propagated by what are called layers, an opera- 



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