44 



FOUNDATIONS 0¥ BOTAlfY 



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 : 



(o) The brown 

 layer of outer bark. 

 (6) 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 

 exposed to the air for 

 a few minutes and 

 changed somewhat in 

 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-ofE 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. 



Fig. 21. — Much Magnified Cross-Section of a 

 Very Young Dicotyledonous Boot. 



h, root-hairs with adhering bits of sand ; e, epidermis ; 

 8y thin-walled, nearly globular cells of bark ; 6, hard 

 bast ; c, cambium ; «?, wood-cells ; d, ducts. 



