152 



BOTANY. 



green in the air ; and by being irresistibly attracted towards 

 the centre of the globe. The part of the root which is united 

 with the trunk is called the neck; the undivided portion suc- 

 ceeding the neck is termed the body, and, finally, the rami- 

 fications are distinguished as radicles. It is thought that the 

 extremity of the radicles presents certain little bladders (spon- 

 geoles) which produce the phenomenon of endosmosis, or that 

 phenomenon in which noxious fluids are thrown off, while 

 nutritive are absorbed. 



The Stem. 



That part of the vegetable which grows in an inverse di- 

 rection with the root, which seeks the air and the light, bears 

 flowers and leaves, and transfers the ascending sap to these 

 latter from the roots. All vascular vegetables possess this 

 organ, but it is sometimes excessively short, as in the Hya- 

 cinth, where it is reduced to a subterranean platform. The 

 spot where the root joins the stem is called the neck. We 

 must not confound with the stem two supports of certain 

 Flowers, both without leaves; the one called scape, issues 

 from the midst of the radical leaves (example, Hyacinth), the 

 other, called radical peduncle, issues from the axil of a leaf. 

 The tissue of the stem has a marked influence upon the ascent 

 of the sap. In fact, water will ascend in a branch which we 

 plunge inverted into a full vessel ; it also mounts with great 

 celerity and force in a slip of Vine, cut at some distance from 

 the earth and stripped of its leaves. Hales, a celebrated 

 English physician, in an experiment of this nature, saw the 

 liquid raise a column of mercury to the height of thirty-eight 

 inches. 



The Trunk. 



The stem of dicotyledonous Trees, such as the Beech, the 

 Oak, &c. It is characterized externally by being conical, 

 that is to say, by tapering from the base to the summit, and 

 by being divided, at its upper part, into boughs, branches, 

 and ramuscules or twigs, bearing leaves and flowers. Exa- 

 mined internally, it exhibits the medullary canal, and, upon 

 the circumference, the ligneous beds and the bark. Its dia- 

 metrical increase is brought about by the annual formation of 



