ABSORPTION OF LIQUID NUTRIMENT. 9 



with a magnification of 10 to 25 diameters and observe the remain- 

 ing soil-particles attached to the irregular root-hairs. 



EXPERIMENT 6. 



STRUCTURE OF ROOT-HAIRS. 



Cut a thin cross-section of the root of a seedling grown in the 

 germinator and examine with a magnification of 50 to 100 diameters. 

 Note the tubelike structure of the hairs, the thin irregular layer of 

 protoplasm on the inner side of the wall and the large transparent 

 central portion filled with sap. Examine the base of the hair and 

 note its relation to the neighboring cells of the root (Fig. 3). 



6. Zone of Root-hairs. As the root extends in length by 

 the growth of a portion near the tip, new root-hairs constantly 

 arise in this region, while the older ones in the region farther 

 away are constantly dying. The zone of root-hairs ordinarily 

 begins I to 3 cm. back of the tip and extends backward along 

 the root for a distance of about 5 to F IG> 5. 



10 cm. In this manner new root-hairs 

 are continually brought into contact 

 with fresh particles of soil. 



EXPERIMENT 7. 



MOVEMENT OF ZONE OF ROOT-HAIRS. 



Place a germinated seed of Pea or 

 Squash in a small funnel or thistle-tube 

 in such manner that the root extends 

 downward in the narrow outlet. Cover 

 the seed with moist cotton and place a 

 layer of moist filter-paper and a glass 



plate over the top of the funnel to prevent A 



Apparatus to demonstrate 

 the seedling from becoming dried. Set progression of zone of 



the funnel upright in a bottle containing root-hairs. (After (Dels.) 

 . . K, potassium hydrate 



a small amount of a solution of potassium solution ; Z, moist filter- 

 hydrate. This solution will absorb the P a P er - 

 carbon dioxide gas given off by the seedling. By means of India 

 ink mark on the glass tube the boundaries of the zone of root- 

 hairs every day during a week. (Fig. 5.) 



