30 



ELEMENTS OF BOTANY. 



starting out as expansions of roots, not of underground stems 

 like those of the potato, Mg. 35, and by the irregularity with 

 which buds appear on their surface, if they appear at all. 



44. Structure of Boots. — The structure of the very young 

 root has been somewhat explained in §§ 17, 18. That of 

 older woody roots of dicotyledons is somewhat more com- 

 plicated. 



Fig. 16.— A Taproot. 



Tia. 17. — Fibrous Roots. FiG. 18. — Fascicled Boots. 



Cut thin transverse sections ^ of large and small roots of any hardwood 

 tree 2 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 hrown layer of outer bark. 



(6) The paler layer within this. 



^ These may be cut with a razor, flat-ground on one aide and hoUow-ground on 

 the other, with a scalpel, or with a regular section-knife. The beginner will prob- 

 ably find much difficulty in getting good sections, but will at any rate soon obtain 

 some which are thin enough on the edges to be fairly transparent. A section of veTy" 

 small area will be as good for making out detail of structure as one which extends 

 all the way across the root. Unless a good deal of time is available for laboratory 

 work, the sections will have to be prepared by the teacher, or they may be bought 

 ready-cut. See Appendix 0. 



2 Toung suckers of cherry, apple, etc., which may be pulled up by the roots, will 

 afford excellent material. 



