CONTENTS OF CELLS. 



are united together. Some maintain that the cell-walls in the young 

 state unite together directly, and become agglutinated, more or less, 



27 



according to their places of contact. Others, as Mohl and Henfrey, 

 hold that there is an intercellular matter which acts as a sort of 

 cement, or Collenchyma (x&'?a, glutinous matter). In sea-weeds, the 

 cells, of which the entire plant is composed, are placed at a distance 

 from each other (fig. 29 a a), and the intervals are filled up by this 

 intercellular substance (fig. 29 ft), which thus forms a large part of 

 their bulk. In the higher classes of plants, when the cells touch 

 each other, the layer of intercellular matter must be very thin, except 

 in the intercellular canals or spaces. Mirbel looks upon it as the re- 





mains of the mucilaginous fluid in which the cells were originally deve- 

 loped, and which has become thickened to a greater or less degree, as 

 in the root of the Date (fig. 30), where a a a indicate the cells, and 

 b b b the interposed substance. 



2. CONTENTS OF CELLS. 



14. The external membrane of cells is composed of the unazotised 

 substance called Cellulose, and in their interior a mucilaginous matter 

 is contained, which undergoes changes in the progress of growth. 



Fig. 27. Cellular tissue, from pith of Elder. 



Fig. 28. Porous Merenchyma, from Houseleek (Sempermvum tectorumi). a, Intercellular canal. 

 Fig. 29. Cellular tissue of Sea-weed (Himanihalia lorea). a a, Cells. 6, Intercellular matter. 

 Fig. 30. Central portion of young root of Date, a a a, Thickened cells, bbb, Intercellular 

 substance of Mirbel. 



