OF THE WOOD. 37 



Mirbel supposes to produce the liber or 

 young bark, and at the same time, by a 

 peculiar arrangement of the vascular parts, 

 the alburnum or new wood. His opinion is 

 strengthened by the observation of a tribe 

 of plants to be explained hereafter, Palms, 

 Grasses, &c. in which there is no real bark, 

 and in which he finds that the woody fibres 

 do actually produce the cambium. Dr. Hope's 

 experiment will scarcely invalidate this opi- 

 nion, because it may be said the cambium 

 had already in that case formed the liber. 



This matter will be better understood when 

 we come to speak of Mr. Knight's experiments 

 on the course of the sap. 



