42 



FOUNDATIONS OF BOTANY 



the entire root with a moderate magnifying power, since 

 the whole is sufficiently translucent to allow the interior 

 as well as the exterior portion to be studied while the root 

 is still alive and growing. 



Place some vigorous cuttings of tradescantia or Zebrina, which' 

 can usually be obtained of a gardener or florist, in a beaker or jar of 



water. 1 The jar should 

 be as thin and trans- 

 parent as possible, and 

 it is well to get a flat- 

 sided rather than a 

 cylindrical one. Leave 

 the jar of cuttings in 

 a sunny, warm place. 

 As soon as roots have 

 developed at the nodes 

 and reached the length 

 of three-quarters of an 

 inch or more, arrange 

 a microscope in a hori- 

 zontal position (see 

 Handbook), and exam- 

 ine the tip and adjacent 

 portion of one of the 

 young roots with a 

 power of from twelve 

 to twent diameters. 



FIG. 20. Lengthwise Section (somewhat diagram- 

 matic) through Root-Tip of Indian Corn, x about 130. 



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

 rating from cap ; s, growing point ; o, epiderm's ; p', 

 intermediate layer between epidermis and central 

 cylinder; p, central cylinder; d, layer from which 

 the root-cap originates. 



Note: 



(a) The root-cap, 



of loosely 



attached cells. 



(&) The central 



cylinder. 



1 If the tradescantia or Zebrina cannot be obtained, roots of seedlings of 

 oats, wheat, or barley, or of red-clover seedlings raised in a large covered cell 

 on a microscope slide, may be used. 



