362 EXPLANATIONS OF THE PLATES. 



running through the stem). , Cells of the pith ; b, vascular bundle 

 composed of elongated cells, and these, proceeding from within 

 outward, having the form of annular, spiral, porous and bass- cells ; 

 c, cells of the rind, the outermost containing some granules coloured 

 by chlorophyll. 



PLATE II. 



ALL THE OBJECTS ARE REPRESENTED GREATLY ENLARGED. 



FIG. 1. Some cells from a Cactus, containing various forms of 

 crystals ; also some loose crystals of different forms. It must be 

 observed, that in Nature these various forms are never assembled so 

 closely together as they have been here, for the sake of occupying 

 less space. 



FIG. 2. The external portion of a delicate transverse section of 

 a grain of Rye. a, Some layers of yellowish flattened cells which 

 form the shell of the grain ; b, the outer layers of cells of the grain ; 

 these are completely filled with a yellowish, mucilaginous matter 

 containing granules ; c, the interior cells of the grain which contain 

 little else but starch granules, and only here and there a little of 

 that granular mucilaginous matter which is what is called the gluten 

 of the meal, and is the most nutritious constituent of Grain. The 

 Bran which is removed in grinding, contains at least all the layers 

 to c ; all the remaining cells, forming the white or fine meal, resemble 

 in form and contents those marked c. 



FIG. 3. Starch granules, from the Potato. 



FIG. 4. Ditto, constituting East Indian Arrow-root. 



FIG. 5. Ditto, genuine West Indian Arrow-root. 



FIG. 6. Ditto, very commonly sold for West Indian Arrow-root. 

 The medicinal properties are exactly similar in both kinds. 



FIG. 7. A small piece of the outer layer of cells from the red- 

 spotted flower-stalk of the greenish-flowered Veltheimia. It is at 

 once seen that the red spots consist of little groups of cells con- 

 taining red sap, those around being filled with green matter. It also 

 affords a striking proof of the independance and perfect continuity of 

 each cell, since otherwise the different coloured juices must become 

 mingled. 



FIG. 8. A fine longitudinal section of Oak-wood, consisting 



