‘44 FOUNDATIONS OF BOTANY 
described in Sect. 106, and a section may look quite unlike 
the young root-section shown in Fig. 21. 
55. Examination of the Root of a Shrub or Tree. —Cut thin 
transverse sections of large and small roots of any hardwood tree! 
and examine them first with a low power of the microscope, as a 
two-inch objective, to get the general disposition of the parts, then 
with a higher power, 
as the half-inch or 
quarter-inch, for de- 
_tails. With the low 
¥ power, note: 
(a) The brown 
layer of outer bark. 
(b) The paler layer 
within this. 
(c) The woody cyl- 
inder which forms 
the central portion of 
the root. 
The distinction be- 
“tween (b) and (c) is 
more evident when 
the section has been 
Fic. 21.—Much Magnified Cross-Section of a exposed to the air for 
Very Young Dicotyledonous Root. a few minutes and 
h, root-hairs with adhering bits of sand; e, epidermis; chan ged somewhat in 
s, thin-walled, nearly globular cells of bark ; b, hard 
bast ; c, cambium ; w, wood-cells ; d, ducts. 
color. It is a good 
plan to look with the 
low power first at a thick section, viewed as an opaque object, and 
then at a very thin one mounted in water or glycerine, and viewed as 
a transparent object. 
Observe the cut-off ends of the ducts, or vessels, which serve as 
passages for air and water to travel through; these appear as holes in 
the section, and are much more abundant relatively in the young 
' 1 Young suckers of cherry, apple, etc., which may be pulled up by the © 
roots, will afford excellent material. 
