406 DEFINITION OF SPECIES. 



fined, or what is termed Glossology (yXueca, a tongue or language, 

 and \6yog, a discourse), and Terminology ("»,(*«, a boundary ; Latin, 

 terminus). The meaning of the terms in this descriptive language 

 must not depend on fancied resemblances, but must have a precise 

 definition, and be constant. In acquiring a knowledge of the conven- 

 tional terms, or of the vocabulary of the science, the student at the 

 same time fixes in his mind the perceptions and notions which these 

 -terms convey, and thus, in reality, becomes acquainted with important 

 elementary facts. 2. A plan of the system, or the principles on 

 which the divisions and subdivisions of the system are made, Diataxis 

 (Sidra.^i;, orderly arrangement), or what is properly called Taxonomy 

 (rd^ig, order, and voftog, law). There have been two great plans pro- 

 posed in Botany, one denominated artificial, the other natural. The 

 first is founded on characters taken from certain parts of plants only, 

 without reference to others ; while the second takes into account aU 

 the parts of plants, and involves the idea of affinity/ in essential organs. 

 3. There must be also the means of detecting the position of a plant 

 in a system, by short diagnostic marks. In doing so, a few essential 

 characters are selected in accordance with natural affinities. The 

 division into genera is a most valuable help in determining plants. 

 Linnaeus did great service to science by his generic divisions, and by 

 adopting a binomial (his, twice, and nomen, a name) system of nomen- 

 clature, in which the genus and species are included in the name of 

 the plant. 



' Species.- — Plants as they occur in nature are viewed as individuals 

 resembling or diflfering from each other. Some individuals are so 

 decidedly alike that we at once give them the same names. Thus, a 

 field of wheat is composed of numerous similar individuals, which can 

 be separated from each other, but cannot be distinguished by any per- 

 manent or marked difference. Although there may be some difference 

 in size and other minor points, still we at once say they are stalks of 

 Wheat. Every grain of Wheat, when sown, produces a stalk of 

 Wheat ; these stalks yield grains, which produce individuals like their 

 parents. The shoots or buds given off from the base of Wheat by 

 tillering also produce stalks of Wheat. On such universal and in- 

 evitable conceptions as these our idea of species is founded. No classi- 

 fication can be made unless the meaning of the term species is defined. 

 By species (as regards the present epoch of the earth's history) we 

 mean an assemblage of individuals having characters in common, and 

 coming from an original Stock or Protoplast. They resemble each 

 other more closely than they do any other plant, so that they are con- 

 sidered as originating from a common parent, and their seeds produce 

 similar individuals. There may be differences in size, colour, and other 

 unimportant respects ; and thus varieties may exist, exhibiting minor 

 differences, which are not, however, incompatible with a common 



