PART II. 



TAXONOMY; 



OB TUB 



CLASSIFICATION OF PLANTS. 



305. To classify requires knowledge of the objects to be class- 

 ed; and the more extensive the knowledge, the more valuable the 

 classification. We might have before us any number of bodies, 

 and class them readily by their color. We might put gold, 

 sulphur, and turmeric in the same class, because they are yellow. 

 Any one, however, acquainted with these substances, would read 

 our ignorance in our classification. Any classification that throws 

 together bodies that are entirely unlike in all important partic- 

 ulars, can have no claim to a scientific or philosophical classifi- 

 cation, however useful it may be in some respects. 



To arrange the individuals which nature presents us, in such 

 a manner, that those, most nearly related in fact, may be con- 

 tiguous in our system, is the true object of scientific classifica- 

 tion. To throw the unnumbered species of plants in groups, 

 and place these groups in the positions with regard to each 

 other that their real nature demands, is the aim of botanical 

 classification. 



306. Nature presents us only with species. All the groups 

 we make are more or less artificial. 



A species includes all those individuals that may be consid- 

 ered as originating from a common parent. Plants arising from 

 seeds, cuttings, grafts, buds, bulbs, or layers, are of the same 

 species as the plant from which they originated. These plants 

 may differ in many respects, more or less, from the parent plant, 

 owing to the different circumstances under which they are pro- 

 duced, thus forming varieties. 



Races are produced by the long-continued application of the 

 causes that produce varieties, so that the variation becomes com- 

 paratively permanent. Races are produced and kept up and 

 varied by the skill of the gardener ; as is exhibited in our 

 grains, cabbages, turnips, peas, beets, <fec. Hybrids are pro- 



