THE ROOT 63 
the office of the stem, until there is practically no difference 
between them. On the sides of gullies, where the earth 
has been washed from around the trees, we often see the 
upper portion of the root covered with a thick bark and ful- 
filling every office of a true stem. 
67. Minute structure of the root. — (a) Mount in water 
and place under the microscope a portion of the root of an 
oat or radish seedling containing a number of hairs. In 
studying the thin, transparent roots of very young seedlings 
a section will not be necessary. Observe whether the hairs 
originate from the epidermis or 
from the interior. Are they true 
roots, or mere outgrowths from 
the cells of the epidermis? Do 
they consist of a single cell or a 
number of cells each? Notice 
what very thin cell walls the 
hairs have ; is there any advan- 
tage in this? The interior, trans- 
parent portion of the hair con- 
tains the sap, and the protoplasm 
forms a thin lining on the inner pg. 79, Se ee 
surface of the wall; why not through the tip of a young root, some- 
the sap next the wall and the bag ef aarmreinend Sal cl 
protoplasm in the interior? (58, ec a Vargercgns Gla 
60.) root cap; d, dead and dying cells loos- 
(b) Next examine a portion ened from the extremity of the cap. 
of the body of the root and try to make out the parts as 
shown in Fig. 79, and compare them with your observa- 
tions in 64. The light line running through the middle is 
the central cylinder, up which the water passes, as was shown 
by the colored liquid in 64. Outside this is a darker por- 
tion (a, Fig. 79), corresponding to the cortex (rr, Fig. 77). 
Besides other uses, the cortex serves to prevent the loss 
of water as it passes up to the stem, and also, in fleshy 
roots like the carrot and turnip, for the storage of nourish- 
