218 ANATOMY AND PHYSIOLOGY OF PLANTS. 



THE BRANCH. 



2. The branches being nothing more than elongated 

 members from the main stem, exhibit nearly the s;ime 

 appearance on dissection, as the trunk from whence 

 they proceed. 



Their apparent use to the vegetable economy is, to afford a more 

 extended snrface for the evelution of leaves. 



THE BULB. 



3. Bulbs, we must first remember, are or* two kinds; 

 the one called radical or root-bulbs, and the other cau- 

 linar or stem-bulbs. 



4. The radical bulbs display themselves, upon anato- 

 mical enquiry, to be of three kinds; all formerly men- 

 tioned under the names of solid, scaly, and coated bulbous 

 roots. 



The solid bulb consists of an external, fibrous, or membranous 

 envelope, separable into two or more layers, and internally of a fine 

 epidermis enclosing a firm but succulent pulp, in the centre of 

 which are lodged the i urtiments of the future plant. The coated bulb 

 is formed of a number of concentric layers, gradually diminishing 

 from the circumference to the centre ; the outer layer may be either 

 a fine and delicate membrane, or of a thick and leathery coat, and 

 the interior layers of a fine epidermis enveloping a succulent pulp, 

 united together by a viscid juice. The scaly bulb will be found to 

 consist externally of the base of the sheathing part of the root-leaves 

 ~of the former year, transformed into the shape of scales, an-l inter- 

 nally of the rudiments of the root-leaves of the following year, with 

 the incipient stem and stem-leaves occupying the centre. 



5. The canlinary bulb is always of a scaly description. 



