xu 



BOTANY. 



and generally have more than one stem) or trees (which have a 

 single stem, and often attain a height of many metres). It must 

 be remembered that intermediate forms of all degrees occur be- 

 tween herbs and shrubs, herbs and trees, and shrubs and trees. 



Duration. — -Some stems live for but one season, and are known as 

 annual; others live for two seasons (gathering food the first, and 

 producing flowers and seeds the second), these are 'biennial; those 

 which live for several or many years are perennial. 



Branching, — Most stems branch more or less, generally irregu- 

 larly, rarely regularly ; the latter may be alternate, opposite, or 

 whorled (i.e., three or more in a circle around the stem). 



The Barl<. — With a sharp knife dissect the bark of a twig, no- 



Fio I. 



Fia. II. 



Fig. I. — Cross-section of the stem of an oak-tree thirty-seven year.s old, show, 

 inpr the annual rings, rtn, the medullary rays; m, the pith (medulla). 



Fig. II. — Cross-section of the stem of a palm-tree, showing the irregularly- 

 placed bundles. 



ticing — 1st. The thin outer part, the epidermis. 2d. A soft layer 

 beneath it, the soft iarJo (which is entirely green, or partly green 

 and partly colored, or more or less corky). 3d. A layer of fhrous 

 tarlc, often called hast. Dissect the bark of older parts of the 

 stem and notice the disappearance of the epidermis and the soft 

 bark. The fibrous bark has here become intermingled with more 

 or less corky matter, and has been ruptured into scales, ridges, 

 and furrows. 



The Wood. — I. With a sharp knife cut across the stem and ex- 

 amine the portion inside of the bark. If of a stem several years 



