158 



ALTERATION OF POSITION. 



this kind in the possession of the writer, and taken 

 fi'om a cavity in an apparently solid block of rosewood ; 

 externally there were no marks to indicate the existence 

 of a central space, but when the block was sawn up 

 for the use of the cabinet-maker, this root-like struc- 

 ture was found in the centre and attached to one end 

 of the cavity. 



The production of roots which ultimately serve as 

 props to support the branches, or as buttresses to com- 

 pensate for the increasing weight of branches and 

 foliage, is also a familiar occurrence. The huge gnaurs 

 and burrs met with occasionally on some trees often 

 produce great quantities, not only of adventitious 

 buds, but of roots also. 



The leaves, equally with the stems, have the power 

 of emitting roots under certain conditions, as when the 

 leaves are in close contact with moist soil or as the 

 result of injury. This happens in some plants more 



Fig. 71. Production of adventitious roots from leaf stalk of celery, 

 readily than in others Bryophyllinn cahjcinnm is a 

 well-known instance. Mr. Berkeley has described the 

 formation of roots from the fractured leaves of celery,^ 



1 Gard. Chron..' 1852, p. 51. 



