ROOT HAIRS 
249 
page 15). They alsc 
serve to fix the plant 
firmly in the soil. 
LABORATORY 
STUDY OF 
ROOTS 
Cut a root of carrot or 
parsnip lengthwise and 
identify (1) dermatogen, 
the epidermal covering; 
(2) cortex, the region 
under the dermatogen; 
(3) plerome, or central 
cylinder. Cut it cross¬ 
wise and identify the same 
regions. Make drawings 
of both sections and label 
fully. In both sections 
look for rootlets and note 
the region from which 
they arise. Show this in 
your drawing. 
Stand cut-off roots of 
parsnip overnight in water tinted with red ink. In what region does 
the color show? Make cross sections of one and longitudinal sections 
of the other. Draw both and describe. 
Look at the roots of seedlings furnished you. How does the extent 
of roots compare with the parts aboveground? 
Examine roots grown in a moist chamber for root hairs. Compare 
with one grown in sawdust or soil after it has been carefully washed. 
How do they differ? On 
what part of the rootlet are 
the root hairs most numer¬ 
ous? Where are they the 
longest ? 
Mark a root with a fine pen 
dipped in India ink, making 
the marks even and close to¬ 
gether (about 1 mm.). Ex¬ 
amine from time to time to 
Figure 238. — Bit of Epidermis of Root 
with Root Hairs. 
Figure 237. — Germinating Wheat, Showing 
Root Hairs. 
Notice the plumule growing up and the roots 
down. This grain of wheat was germinated in 
moist air, and not in the soil. Root hairs are 
seldom seen in soil grown seedlings, as they 
are so fragile that they break off and remain in 
the soil when the seedling is removed. 
