70 THE MECHANICAL FUNCTIONS. 



hardly be supposed to adhere in every point, we 

 may expect to find that spaces have been left 

 in various parts between them ; and that com- 

 munications exist to a certain extent between 

 all these spaces ; so as to compose what may 

 be regarded as one large cavity. These have 

 been denominated the intercellular spaces ; and 

 they have been supposed to perform, as will 

 hereafter be seen, an important part in the func- 

 tion of Nutrition. 



Fluids of different kinds occupy both the cells 

 and the intercellular spaces. The contents of 

 some is the simple watery sap ; that of others 

 consists of peculiar liquids, the products of 

 vegetable secretion : and very frequently they 

 contain merely air. In many of the cells there 

 are found small opaque and detached particles 

 of the substance termed by chemists, Fecula, of 

 which starch is the most common example. In 

 several parts, and more especially in the leaves, 

 and in the petals of flowers, the material which 

 gives them their peculiar colour is contained in 

 the cells in the form of minute globules. De 

 Candolle has given it the name of Chromule* 



The cells of the ligneous portion of trees and 

 shrubs are further encrusted with particles of a 

 more dense material, peculiar to vegetable organ- 

 ization, and termed Lignine. It is this substance 



* Organographie, Tom 1, p. 19. 



