SO DESCRIPTIVE BOTANY. PART I. 



from seeds of the same common stock. Where these 

 individuals differ in certain respects among themselves, 

 they are termed " varieties ; " but all varieties of the 

 same species may, under particular circumstances, be 

 produced from the seeds of one plant. When different 

 species bear a striking resemblance to each other, they 

 are classed together in a group which is termed a 

 "genus;" and such genera as agree in several points, 

 form a higher group called an " order ; " and those 

 orders which are most nearly related, constitute our 

 chief or primary groups, termed " classes. " Minor 

 groups of subordinate value may be formed in each of 

 these ; but we do not consider it necessary at present 

 to enter into further details of this kind. We merely 

 propose to explain some of the chief characters by 

 which all plants may be grouped under three distinct 

 classes. The considerations upon which these groups 

 depend, do not rest upon any one solitary fact relative 

 to the structure or functions of all the species they 

 contain ; for there is no leading characteristic in either 

 class which is not liable to some objection, if it were to 

 be considered as the only distinguishing mark for de- 

 ciding the claims of a species to be included in that 

 class. But where one leading characteristic is deficient 

 in one species, and another in another, it is from the 

 aggregate of such as are present that we must de- 

 cide upon the class to which each should be referred. 

 With very few exceptions, however, nearly all plants 

 may be referred by any botanist, at a single glance, and 

 with unerring certainty, to their proper class ; and a 

 mere fragment even of the stem, leaf, or some other 

 part, is often quite sufficient to enable him to decide 

 this question. The names of these three classes are 

 derived from one of the chief characteristics which 

 prevails through nearly all the species included under 

 each of them separately. This we shall presently ex- 

 plain ; but the reader may understand these names to 

 be Dicotyledones, Monocotyledones, and Acotyledones ; 

 and that the two former of these classes have respect- 



