210 



SCIENCE OF AGRICULTURE. 



Part II, 



Chap. II. 



Vegetable Anatomy, or the Structure and Organization of Plants. 



1278. Vegetables may be classed for the study of their anatomy and physiology, according 

 as they are distinguished by a structure or organization more complicated or more simple. 

 The former will constitute what may be denominated perfect plants, and will form a 

 class comprehending the principal mass of the vegetable kingdom. The latter will con- 

 stitute what may be denominated imperfect plants, and will form a class comprehending 

 all such vegetables as are not included in the foregoing class. We shall first consider 

 their external, and next their internal organization. 



Sect. I. Of the External Structure of Perfect Plants. 



1279. The parts of perfect plants may be distributed into conservative and reproduc- 

 tive, as corresponding to their respective functions in the economy of vegetation. 



1 280. The conservative organs are such as are absolutely necessary to the growth and 

 preservation of the plant, and include the root, trunk, branch, leaf, and frond. 



1281. The root is that part of the plant by which it attaches itself to the soil in which it grows, or to 

 the substance on which it feeds, and is the principal organ of nutrition. 



1282. The trunk is that part of the plant which, springing immediately from the root, ascends in a 

 vertical position above the surface of the soil, and constitutes the princij)al bulk of the individual. 



1283. TTie branches are the divisions of the trunk, originating generally in the upper extremity, but 

 often also along the sides. 



1284. The leaf, which is a temporary part of the plant, is a thin and flat substance of a green color, 

 issuing generally from numerous points towards the extremities of the branches, but sometimes also imme- 

 diately from the stem or root, and distinguishable by the sight or touch into an upper and under surface, 

 a base and apex, with a midrib and lateral nerves. 



1285. The frond, which is to be regarded as a compound of several of the parts already described, con- 

 sists of an union or incorporation of the leaf, leaf-stalk, and branch or stem, forming as it were but one 

 organ, of which the constituent parts do not separate spontaneously from one another by means of the 

 fracture of any natural joint, as in the case of plants in general, but adhere together even in their decay. 

 It is found in palms and ferns. 



1286. The conservative appendages are such accessory or supernumerary parts as are 

 found to accompany the conservative organs occasionally, but not invariably. They are 

 permanent in whatever species they are found to exist ; some being peculiar to one 

 species, and some to another. But they are never found to be all united in the same 

 species, and are not necessarily included in the general idea of the plant. They are 

 denominated gems, glands, tendrils, stipulse, armature, pubescence, and anomalies. 



1287. Gems or bulbs are organized substances issuing from the surface of the plant, and containing the 

 rudiments of new and additional parts which they protrude ; or the rudiments of new individuals which 

 they constitute by detaching themselves ultimately from the parent plant, and fixing themselves in the 

 soil. 



1288. Glands are small and minute substances of various different forms,found chiefly on the surface of 

 the leaf and petiole, but often also on the other parts of the plant, and supposed to be organs of secretion. 



1289. The tendril is a thread-shaped and generally spiral process issuing from the stem, branch, or 

 petiole, and sometimes even from the expansion of the leaf itself, being an organ by which plants of 

 weak and climbing stems attach themselves to other plants, or other substances for support; for which 

 purpose it seems to be well fitted by nature, the tendril being much stronger than a branch of the same 

 size. 



1290. The stipules are small and foliaceous appendages accompanying the real leaves, and assuming the 

 appearance of leaves in miniature. 



1291. Ramenta are thin, oblong, and strap-shaped appendages of a brownish color, issuing from the 

 surface of the plant, and somewhat resembling the stipulte, but not necessarily accompanying the leaves. 



1292. The armature consists of such accessory and auxiliary parts as seem to have been intended by 

 nature to defend the plant against the attacks of animals. 



1293. The pubescence is a general term, including under it all sorts of vegetable down or hairiness,Vith 

 which the surface of the plant may be covered, finer or less formidable than the armature. 



1294.. Anomalies. There 

 are several other appen- 

 dages proper to conser- ^<tt^ 217 

 vative organs, which are 

 so totally different from 

 all the foregoing, that 

 they cannot be classed | 

 with any of them ; and 

 so very circumscribed in 



their occurrence, that -"i^n^^j^-sss/ /y 



they do not yet seem to ^^^^6^5^ <* 



have been designated by 

 any peculiar appellation. 

 The first anomaly, as af- 

 fects the conservative ap- 

 pendages, occurs in dio- 

 noea mnscipulaor Venus 's 

 fly-trap (Jig. 217 a). A 

 second is. that which oc- 

 curs in sarracenia pur- 

 purea or purple side-sad- 

 dle-flower (6). A third, which is still more singular, occurs in nepenthes distillatoria (c). The last anomaly 



