216 



LINK ON CELLULAR TISSUE. 



leaves, in the flower scales, the flower cups, &c, and especially where 

 one part is attached to another, as in the flower scale of the Scirpus 

 maritimus. 



6. Pulp Tissue. — The cells are neither spherical, cylindrical, nor pris- 

 matic ; but of an oval or oblong form. This tissue is common in the 

 interior bark of trees, in the pulp, (for which reason I have called it the 

 pulp tissue), and especially between the fibrous vessels, besides the 

 air vessels, as in the interior bark of a root of the Malva crispa. 



These six varieties of the cellular tissue admit of several varieties, and 

 intermediate forms are often found, which seem to partake of two 

 varieties. A seventh variety might be added, the compact tissue, which 

 is found in some mushrooms, lichens, &c. ; but this tissue is scarcely 

 evolved, or rather it is so fine, that the structure of it cannot be distin- 

 guished. 



The arrangement of cells is generally alternate, and the rows are 

 parallel to the length of the part in which they are found. Some- 

 times these rows are arranged crosswise. I have found this arrange- 

 ment in leaves when they are cut in a direction perpendicular to 

 the surfaces, which it is very difficult to do, especially when the leaves 

 are thin ; but in the latter this arrangement is more distinct than in 

 succulent leaves, where they are usually absent. 



They are found in the young leaf just unfolded. These cross fibres 

 are seen in the middle of the wood, and on the surface of the large 

 roots of the Malva crispa. They are not found in the small roots, and 

 I am sure that they are formed by the enlargement of the root, which 

 spreads the bark, and draws aside the meshes of the net-work which 

 forms the cells. Take a net made of thread, stretch it sideways, and 

 you will see the meshes arrange themselves in horizontal rows in a 

 manner similar to that which we have just described. 



The cell increases in size with the rest of the plant. It is astonish- 

 ing that a cell, surrounded by wood, should spread itself, notwith 

 standing the resistance which the latter opposes to it. All organised 

 bodies evolve themselves and grow by a strong power, and the plant in 

 its evolution breaks a strong thread which may be tied around it. 



Each cell is a separate organ, destined to preserve and prepare the 

 pulp which is destined to furnish the other parts. The superfluous part 

 penetrates into the Meatus intercellular es, and somewhat resembles the 

 fat of animals. The green matter by which plants are coloured is 



