320 COMPOSITE ORGANS. CHAP. 11. 



of intermixture with other parts, by which its 

 natural structure is always somewhat affected. Its 

 structure is, however, pretty fairly represented in 

 one or other of the above descriptions in almost all 

 its different aspects, but the description which I 

 have found to be the most accurate and the most 

 generally applicable, is that of M. Mirbel, in which 

 he compares it to clusters of small and hexagonal 

 cells or bladders containing for the most part a 

 coloured juice, and formed apparently of the fold- 

 ings and doublings of a fine and delicate membrane, 

 in which no traces of organization are to be dis- 

 tinguished. 



Whodi- But M. Mirbel, in the detail of his investiga- 

 imo her- tions, institutes also the following distinctions : In 



ma. 



tissue and ^ ie trun ^ ^ wnat are called dicotyledonous plants, 

 parenchy- he regards the pulp, or to use his own appellation 

 the Cellular tissue, as consisting of two distinct 

 portions, which he designates by the respective ap- 

 pellations of the Herbaceous tissue, and the Paren- 

 chyma. The former is the exterior portion of the 

 cellular tissue, of which the cells always contain a 

 resinous and coloured juice, that communicates its 

 peculiar tinge to the epidermis. The latter is the 

 interior portion of the tissue, composed also of cells, 

 but differing from those of the herbaceous tissue in 

 containing only a watery juice without colour, 

 because it has not been exposed to the action of the 

 light, though in the calyx and fruit this watery 

 juice is said to be also often coloured. But this is 



