THE VJEOETABLE CELL. 



S3 



Transverse section tliroiig^li the albumen of So- 

 pJiGra japomca , cj, intercellular substance , by cavity 

 of the cells. 



tlie intercellular passages, but usually forms a dense mass in it 

 and quite obliterates its cavity. This occurs in remarkable quan- 

 tity in tlie tissue of many Algse, especially of the Fucoide^, the 

 Nostochineae, in the cortical 

 layer of many Lichens, in i^^>. 36. 



the Albumen of many Legu- ,| a 



minos^, e, </., Sophora japo- 

 nioa (%. 36), Gleditschia, &c. 

 It is found in smaller quan- 

 tity, and therefore less readily 

 perceptible, in the intercellu- 

 lar passages of wood, e. g., of 

 Pinvbs (fig. 22) and Buxus, as 

 well as in the intercellular 

 substance of bark. The mass 

 composing the intercellular 

 substance usually resembles 

 so much the substance of the 

 cell-walls between which it 

 lies, that the application of 

 re-agents, as of iodine and 

 sulphuric acid, does not af- 

 ford any certain means of 



accurately distinguishing it from cell-membrane ; in other cases 

 the boundary line between them is very sharply defined. 



An analogous secreted layer, appearing in the form of a mem- 

 brane, occurs upon the surfiice of freely exposed cells ; it possesses, 

 like the outermost membrane of wood-cells, the property of resist- 

 ing obstinately the solvent power of sulphuric acid To this be- 

 long the outer membrane of spores and pollen-grains and the cuticle 

 (fig. 37, a), which invests the whole 

 of the surface exposed to the air j?^^, 37. 



of the higher plants, in the form 

 of a connected membrane. 



Ohserv. When I propounded the 

 theory of the intercellular substance 

 {^^Illustrations and Defenee of my 

 View of the StTUcture of Vegetable 

 SuhstancBj' 1836), this appeared to me 

 to possess a far greater importance in 

 the vegetable organism, than it proved 

 to have suhsequently on more accu- 

 rate investigation of this substance itself and more minute research 

 into the development of cells. I did not perceive that the intercellular 

 substance is a product of the cell, and thought I had discovered in it an 

 universally distributed mass, in which the cells are imbedded, and which, 

 in many cases, exists before the formation of the cells. The real condition 

 is in most cases decidedly the reverse , hut it is not yet, however, clearly 



Cells of the epidermis of the leaf of Ilelle-' 

 hwm fositidus. a, cuticle. 



