36 



ESSENTIALS 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 

 p ^ found to have in- 



, ".-P ~7^ . , , ^ , , ,. 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. 



Fig. 18. Lengthwise Section (somewhat dia- 

 grammatic) through Root-Tip of Indian Corn. 

 X about 130. 



to, root-cap; i, younger part of cap; z, dead cells 

 separating from cap ; «, growing point ; o, epi- 

 dermis ; p', intermediate layer between epidermis 

 and central cylinder ; p, central cylinder ; rf, layer 

 from which the root-cap originates. 



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 hig'her power, as the 

 half-inch or quarter- 

 inch, for details. With 

 the low power, note : 



(a) The brown layer 

 of outer bark. 



(J) The paler layer within this. 



(c) The woody cylinder which forms the central portion of the root. 



1 Young suckers of cherry, apple, etc., which may be pulled up by the 

 roots, wUl afford excellent material. 



