36 ELEMENTS OF BOTANY 
former serving as channels for air and water, the latter 
(and w also) giving toughness to the root. 
Roots of shrubs and trees more than a year old will be 
Fic. 18. Lengthwise Section (somewhat dia- 
grammatic) through Root-Tip of Indian Corn. 
* about 130, 
w, root-cap; /, younger part of cap; z, dead cells 
separating from cap; s, growing point; 0, epi- 
dermis; p’, intermediate layer between epidermis 
and central cylinder; p, central cylinder; @, layer 
from which the root-eap originates. 
(b) The paler layer within this. 
found to have in- 
creased in thickness 
by the process 
described in Sect. 
88, and a_ section 
may look quite un- 
like the young root- 
section shown in 
Fig. 19. 
46. Examination of 
the Root of a Shrub or 
Tree. — Cut thin trans- 
verse 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 details. With 
the low power, note : 
(a) The brown layer 
of outer bark. 
(c) The woody eylinder whieh forms the central portion of the root, 
1 Young suckers of cherry, apple, ete., which may be pulled up by the 
roots, will afford excellent material. 
