154 SYSTEMATIC BOTANY. 



496. Species ( 27). When He called plants into existence 

 in their own specific forms, He endowed each with the power of 

 perpetuating its own kind and no other; so that they have 

 descended to us distinguished by the same characters and prop- 

 erties as at the beginning. When, therefore, the student has 

 formed acquaintance with any one individual plant, he is also ac- 

 quainted with all other individuals belonging to the same species 



4!I7. For example: a single plant of White Clover is a true representative of all the mil- 

 lions of its kind that grow on our hills and meadows. Likewise, a single description ol 

 the White Pine will answer in all essential points for every individual tree of that nobk- 

 species in all its places and times. Thus all the individual plants of the globe are grouped 

 into species by descent and resemblance. 



498. Genera ( 29). Although the species are separated 

 from each other by clear and definite distinctions, still they are 

 found to exhibit, also, constant affinities whereby they stand 

 associated into larger groups called genera. Thus the White 

 Jlover and the Red Clover (Trifolium repens and T. pratense) 

 are universally recognized as different species, but of the same 

 kind or genus ; and a proper generic description of one plant of 

 the genus TRIFOLIUM will convey intelligence to a certain extent 

 concerning every other plant belonging to its 150 species. 



409. Orders. But natural affinities do not end here. The genera are yet too nnmerous 

 for the ready and systematic study of the naturalist. He, therefore, would generalize still 

 further, and reduce th genera to still fewer and broader groups. On comparing the gen- 

 era with each other, he finds that they also possess in common certain important charac- 

 ters which are of a more general nature than those which distinguish them from each 

 other. By these general characters the genera are associated into Orders. 



500. For example: comparing such genera as the Mustard, Radish, Cabbage, Cress, 

 Wallflower, etc., it is seen that, while they differ sufficiently in their generic characters, 

 yet they all have certain marked resemblances in their didynamous stamens, siliquous 

 fruit, whereby they are obviously associated into the same Order the Cruciferse. So, 

 also, the Pines, the Spruces, the Cedars, the Larches, and the Cypress, while as genera 

 they are obviously distinct, yet all bear cones of some form, with naked seeds ; hence 

 they are naturally grouped into one Order the Coniferse. 



501. Classes. In like manner the Orders, by traits of resemblance still more general, 

 are associated into a few groups, each of great extent, called Classes. 



502. Intermediate Groups, formed on the same principles, are recognized as 

 Snbgenera, Suborder* or Tribes, and Subclasses or Cohorts, which will be particularly 

 noticed iii another place. Of the same nature, also, are Varieties, which are groups sub- 

 ordinate to species, already described in 28. 



503. Systems. Two independent and widely different meth 

 ods of classifying the genera have been generally approved the 

 Artificial Method of Linnaeus, and the Natural System of Jussieu. 

 The former is founded solely on characters relating to the organs 



