THE PARTS OF THE SEEDLING. 



13 



ing glass, then as opaque objects in a cell under a low power 

 of the miscroscope ; finally cut off a very small portion of the 

 root with its hairs and examine in water with a power of 160 

 to 200 diameters.* 



Make several sketches of the root-hairs and compare with 

 Figs. 5 and 19. Notice that they do not cover all portions 



h— 



Fig. 3. —Lengthwise Section througli Tip of a Eoot of Barley. (Much magnified.) 



a, thick outer wall of epidermis ; b (portion bounded hy the heavy Une), the central 



cylinder of the root ; c, the growing-point, from which the root-cap is produced 



(in tliis and similar plants) and from which growth in length proceeds ; d, loose 



cells of the root-cap. 



of the rootlets. Where are they most abundant ? Observe 

 that each hair is in reality a very slender tube, closed at the 

 ends, and with walls of extreme thinness. 



The root-hairs in plants growing under ordinary conditions 



1 Great care is needed to prevent the root-hairs from becoming distorted by 

 pressure, and they shrivel up in dry air almost at once. 



