210 SCIENCE OF AGRICULTURE. Part II. 



1301. Taxonomy, or the classification of plants, is the last part of the study of techno- 

 logical botany. It is very evident, that, without some arrangement, the mind of man 

 would be unequal to the task of acquiring even an imperfect knowledge of the various 

 objects of nature. Accordingly, in every science, attempts have been made to classify 

 the different objects that it embraces, and these attempts have been founded on various 

 principles : some have adopted artificial characters ; others have endeavoured to detect 

 the natural relations of the beings to be arranged, and thus to ascertain a connection by 

 which the whole may be associated. In the progress of zoology and botany, the fun- 

 damental organs on which to found a systematic arrangement have been finally agreed on. 

 In both, those which are essential, and which discover the greatest variety, fonn the basis 

 of classification. Animals are found to differ most from each other in the organs of nu- 

 trition, plants in the organs of reproduction. 



1302. Two methods of arranging vegetables have been distinguished by botanists, the natural and 

 the artificial. A natural method is that which, in its distribution, retains all the natural classes ; that 

 is, groups into which no plants enter which are not connected by numerous relations, or which can be dis- 

 joined without doing a manifest violence to nature. An artificial method is that whose classes are not 

 natural, because they collect together several genera of plants which are not connected by numerous 

 relations, although they agree in the characteristic mark or marks assigned to that particular class or 

 assemblage to which they belong. An artificial method is easier than the natural, as in the latter it is 

 nature, in the former the writer, who prescribes to plants the rules and order to be observed in their dis- 

 tribution. Hence, likewise, as nature is ever uniform, there can be only one natural method ; whereas 

 artificial methods may be multiplied almost ad infinitum, according to the different relations under which 

 bodies are viewed. 



1303. The object of the natural method is to promote our knowledge of the vegetable kingdom by g:ene. 

 ralising facts and ideas ; the object of the artificial method is to facilitate the knowledge of plants as indi- 

 vidual objects. The merits of the former method consist in the perfection with which plants are grouped 

 together in natural families or orders, and these families grouped among themselves ; the merits of the 

 latter consist in the perfection with which they are arranged according to certain marks by which their 

 names may be discovered. Plants arranged according to the natural method may be compared to words 

 arranged according to their roots or derivations ; arranged according to an artificial method they may be 

 compared to words in a dictionary. The success attending attempts at botanical arrangement, both 

 natural and artificial, has been singularly striking. Linnaeus has given the most beautiful artificial 

 system that has ever been bestowed by genius on mankind ; and Jussieu has, with unrivalled ability, 

 exhibited the natural affinities of the vegetable kingdom. For the study of this department we refer to 

 the works of Smith, Lindley, DecandoUe, and Gray, but especially to the Encyclopaedia of Plants. 



Chap. II. 



Vegetable Anatomy, or the Structure and Organisation of PiantS' 



1 304 . Vegetables may be classed for the study of their anatomy and physiology, accordingly 

 as they are distinguished by a structure or organisation 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 constitute 

 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, organisation. 



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



1305. The parts of perfect plants may be distributed into conservative and reproduc- 

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



1306. 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. 



1307. 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. 



1308. The trunk is that part of the plant which, springing immediately from the root, ascends in a ver- 

 tical position above the surface of the soil, and constitutes the principal bulk of the individual. 



1309. The branches are the divisions of the trunk, originating generally in the upper extremity, but 

 often also along the sides. 



1310. The leaf, which is a temporary part of the plant, is a thin and flat substance of a green colour, 

 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, witli a midrib and lateral veins or nerves. 



1311. The frond, which is to be regarded as a compound of several of the parts already described, con- 

 sists of a 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. 



1312. 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 de- 

 nominated gems, glands, tendrils, stipulse, ramenta, armature, pubescence, and anomalies. 



