THE ROOT 65 



by the roots to the stem. Each set of these tubes, together 

 with a number of smaller ones belonging to the same group, 

 constitutes a fibrovascular bundle a very important ele- 

 ment in the structure of all roots and stems, as these bundles 

 make up the conducting system of the plant body. 



IV. THE WORK OF ROOTS 



MATERIAL. Germinating seedlings of radish, bean, corn, etc. ; a 

 potted plant of calla, fuchsia, tropseolum, touch-me-not (Impatiens), or 

 corn; a plant that has been growing for some time in a porous earthen 

 jar. 



APPLIANCES. Glass tumblers ; coloring fluid ; wax ; some coarse net- 

 ting; dark wrapping paper, or a long cardboard box; a sheet of oiled 

 paper ; some half-inch glass tubing ; a few inches of rubber tubing ; an 

 ounce of mercury ; some blue litmus paper ; a flower pot full of earth ; 

 a few handfuls of sand, clay, and vegetable mold; a pair of scales; a 

 half dozen straight lamp chimneys, or long-necked bottles from which 

 the bottoms have been removed as directed in Exp. 53. 



EXPERIMENT 43. USE OF THE EPIDERMIS. Cut away the lower end 

 of a taproot; seal the cut surface with wax so as to make it perfectly 

 water-tight, and insert it in red ink for at least half the remaining length, 

 taking care that there is no break in the epidermis. Cut an inch or two 

 from the tip of the lower piece, or if material is abundant, from another 

 root of the same kind, and without sealing the cut surface, insert it in red 

 ink, beside the other. At the end of three or four hours, examine longitu- 

 dinal sections of both pieces. Has the liquid been absorbed equally by 

 both ? If not, in which has it been absorbed the more freely ? What con- 

 clusion would you draw from this, as to the passage of liquids through 

 the epidermis? 



From this experiment we see that the epidermis, besides protecting the 

 more delicate parts within from mechanical injury by hard substances 

 contained in the soil, serves by its comparative imperviousness to prevent 

 evaporation, or the escape of the sap by osmosis as it flows from the root 

 hairs up to the stem and leaves. 



EXPERIMENT 44. To SHOW THAT ROOTS ABSORB MOISTURE. Fill two 

 pots with damp earth, put a healthy plant in one, and set them side by 

 side in the shade. After a few days examine by digging into the soil with 

 a fork and see in which pot it is drier. Where has the moisture gone ? 

 How did it get out ? 



