THE TISSUES. 



127 



compactly filling it. Starch is nutritive matter, sealed up for 

 preservation and future use. 



333. Gum, sugar, salts, acids, alkalies, poisons, medicines, whatever is peculiar in the 

 properties of each vegetable substance, may also be held in solution in the cell-sap, and 

 invisible, unless forming Raphides, little bundles of crystals, needle-shaped, or. of some 

 other form, seen in the cells of Rhubarb, Cactus, Hyacinth. 



. 483. Cells of Potato containing starch-grains. 484, Starch-grains from the Potato. 

 185, from the E. Indian Arrowroot. 486, Raphides, acicular crystals, in a cell of Polyanthes tuberosu. 

 487, Crystals in a cell of Cactus. 488, Cells from the pulp of Pear, coated internally; a longitudinal 



from W. In 



tion ; 489, Transverse section. 490, Starch granules 



dian Arrowroot. 



384. The growth of the plant, then, consists of the development of new cells. This ie 

 accomplished within the pre-existing cells, and by the agency of their contents. The 

 primordial utricle divides itself into two or more utricles, by new walls growing from its 

 sides until they meet. These then acquire the cellulose layer outside, the cytoblast in 

 side, at the expense of the old cell, which shortly gives place to its now progeny. Thus 

 cells multiply, and by millions on millions build up the fabric of the plant. 



Review 3f>8. What composes all vegetable structures ? 361). How is the cell defined ? 

 370. What its primary form ? Mention three varieties. 371. Whence the casual forms? 

 W T hat are they ? 372. What of size ? How many in a cubic inch ? What of Flax cells ? 

 373. Describe the cell-wall. How bring the primordial utricle to view (as in 472) ? Is the 

 wall porous? 375. What appearance of the third layer? 376. What fills up the wood- 

 cells ? How do pitted cells appear? 377. Describe the wonderful structure of spiral cells. 

 Show them (475). 378. Show annular cells in 478, and where else ? Scalariform ? 379. 

 What the material of the outer wall ? Its elements ? Elements of the inner wall ? What 

 within the cell ? 381. What the chlorophyl ? Condition of the coloring matter? 382. 

 Describe the starch granules. 383. The raphides. 384. How do plants grow ? 



CHAPTER II. 



THE TISSUES. 



385. One-celled plants. The cell, as heretofore described, 

 is endowed with a life within itself. It can imbibe fluids, nour- 

 ish itself, and reproduce others like itself. It may, therefore, 

 and actually does in some cases, exist alone as a plant ! Many 

 species of the Confervoids and Diatomes are plants consisting 



