A MANUAL OF BOTANY 17 



Many miscellaneous roots, for drugs, dyes, and other 

 manufactures. 



SECTIOX IV. STUDY OF STEMS 

 1. The Winter Twig, External Features 



General statement. Twigs of hickory and butternut are 

 particularly good for this purpose, although almost any twig 

 will do, if occasion demands. Twigs may be gathered at 

 any time after the leaves fall and kept in sawdust or sand, 

 in the cold. The student ought to be encouraged to study the 

 twigs on the tree, and at first hand learn their individual 

 characteristics. Simple keys may be made for this purpose. 



Surface features. Observe the surface color of the twig 

 in all its length. How does it vary and what may be 

 the explanation? Examine the epidermis and determine 

 whether it is rough or smooth, dull or shining. Some twigs 

 are hairy or downy. Besides these general features you 

 ought to be able to find four special features on the twig, 

 viz. : (1) buds ; (2) leaf -scars ; (3) lenticels ; (4) zones. 



1. Buds. According to their position, buds are terminal 

 (apicaT) and lateral. What, in the hickory, is the difference 

 in the size of these two kinds ? Further, how do the lateral 

 buds vary in different parts of the year's growth ? What 

 explanation can you give for these differences in size? 

 Other twigs show similar variation in greater or less degree. 

 Examine a bud and observe the covering of scales. Are these 

 few or many in number ? How are they arranged with 

 reference to each other ? What is their color ? This is 

 often very characteristic of the special kind of tree. What 

 sort of surface has the scale? It may be smooth, downy, 

 hairy, or varnished. What purpose have these special 

 features ? 



Make a long section tlirough an apical bud and study 

 (m). Observe the cut edges of the scales and, in particular, 



