460 BOTANY. 



Various systems have been proposed in botany, as well as in 

 other branches of Natural History, for the classification of its 

 numerous objects. Already nearly 60,000 species of plants 

 are known ; and if each were distinguished by individual terms 

 implying its place in the system, the acquisition even of the 

 names would be an intolerable load on the memory. Hence 

 has arisen the necessity of generalization. A number of species 

 possessing certain characters in common, though individually 

 distinct, have been arranged under one term including them 

 all, which forms a genus. In comparing generic characters to- 

 gether, groups of these agreeing in certain other particulars, 

 form what is called an order or family ; and orders or families 

 corresponding in some certain distinctive characters form a class. 

 This branch of Botanical Science is termed Taxonomy, or the 

 theory of classification. 



Whatever method the student may fall on to arrive at the 

 knowledge of a species, it is necessary that he study successive- 

 ly the various organs which furnish the characters of the five 

 principal divisions, viz. the class, order, family, genus, and 

 species. In almost all the methods proposed, the organs of fruc- 

 tification have formed the bases of arrangement, as being the best 

 known, and the most conspicuous. Such were the foundation of 

 the systems of Tournefort, Linnaeus, and Lamarck ; and though 

 professedly artificial, the characters derived from these organs 

 brought together groups in many cases very natural. The 

 system of Jussieu, or the Natural Method, is arranged on other 

 principles. 



Joseph Pitton Tournefort, born at Aix, in Provence, pub- 

 lished his Elements of Botany in 1694. He established his 

 method upon the character of the flower or corolla, as being the 

 most striking part of a plant. He divided the vegetable king- 

 dom into two great sections, Herbs and Trees ; the first, com- 

 prehending annual or perennial plants, the stems of which fade 

 in winter, and of which the consistence was not ligneous ; and 

 the second, including all the plants of a woody consistence, 

 which grew to the height of a man, which had buds, and 

 which generally survived more than two years. They were 

 next divided into such as had or had not a corolla ; and these 

 last into those with simple or compound flowers. Those with 

 the flower or corolla t>f one piece were termed monopetalous 



