14 CELLULAR TIfeSUE. 



but the swollen starcli-grains which compose this important 

 vegetable : the beet, carrot, and turnip owe their value, so far 

 as the}^ are suited for food, to the abundance of this tissue, de- 

 veloped in the cellular integument of the bark of the roots, and 

 just in proportion as the other forms are developed, those vegeta- 

 bles become useless. The tough, fibrous form these roots some- 

 times assume in dry seasons, in poor soil, or in an uncultivated 

 state, is owing to the diminished quantity of the cellular tissue 

 proper, and the abundance of the prosenchymous or woody form. 

 Starch, arrowroot, <fec., are but forms of the same substance. The 

 various fruits are composed of cells filled with the various juices 

 peculiar to each species. In the lemon we find the vesicles filled 

 with an acid of considerable intensity. The orange and pine- 

 apple gratify our taste by the mild yet delicious flavor of their 

 contents. In the melon we meet with a fluid of a blandness 

 and insipidity almost equalling fountain water. The various 

 coloring materials drawn from the vegetable kingdom, and used 

 in the arts, have their locality in the same tissue. The coloring 

 matter which produces the great variety of hues that elicit our 

 admiration by their brilliancy and variety, is deposited in trans- 

 parent cells. The satin-like appearance exhibited by many highly 

 colored flowers, depends (according to Lindley) on the highly 

 colored fluid within the cell gleaming through the white shining 

 Pig II membrane of the tissue ; and the peculiar 



appearance of a petal, by which any one 

 readily distinguishes it from a leaf, is oc- 

 casioned by the irregular arrangement of 

 the cells that form its epidermis, some 

 A petal. being more elevated than others, (Fig. 11). 



I9i Crystals are sometimes found in the interior of cells. 

 They are usually called Raphides [rajjkis, a needle) ; which term, 

 however, is strictly applicable only to the needle-like crystals, 

 abundant in many plants. Fig. 12 6. Fig. 12. 



They may be readily seen in the 

 Rhubarb or Onion. Other forms of 

 crystals are found in cells and in other 

 intercellular spaces, Fig. 12 a. The 

 most common substance found crys- "''"'*^ 



tallized is Oxalate of Lime. Crystals in ceiis. 



20. The cell originates in a mucilaginous fluid, which be- 

 comes turbid by minute granules which collect in masses, 



Illustrate it by examples. To wliat is the color of petals owiiiir? To 

 what their peculiar appearance ? —19. \Yhere are crystals sometimes found ? 

 What substance is most common ? — 20. How does the cell originate 1 



