XXVI INTRODUCTION. 



Chap. II. Classification, oe Systematic Botany. 



176. It has already been observed (3) that descriptions of plants should, as nearly 

 as possible, be arranged under natural divisions, so as to facilitate the comparison of 

 each plant with those most nearly allied to it. The descriptions of plants here alluded 

 to are descriptions of species ; the natural divisions of the Flora refer to natural groups 

 of species. 



177. A Species comprises all the individual plants which resemble each other suffi- 

 ciently to make us conclude that they are all, or may have been all, descended from a 

 common parent. These individuals may often differ from each other in many striking 

 particulars, such as the colour of the flower, size of the leaf, etc., but these particulars 

 are such as experience teaches us are liable to vary in the seedlings raised from one 

 individual. 



178. When a large number of the individuals of a species differ from the others in 

 any striking particular they constitute a Variety. If the variety generally comes 

 true from seed, it is often called a Race. 



179. A Variety can only be propagated with certainty by grafts, cuttings, bulbs, 

 tubers, or any other method which produces a new plant by the development of one 

 or more buds taken from the old one. A Mace may with care be propagated by seed, 

 although seedlings will always be liable, under certain circumstances, to lose those 

 particulars which distinguish it from the rest of the species. A real Species will always 

 come true from seed. 



180. The known species of plants (now near 100,000) are far too numerous for the 

 human mind to study without classification, or even to give distinct single names to. 

 To facilitate these objects, an admirable system, invented by Linnaeus, has been uni- 

 versally adopted, viz. one common substantive name is given to a number of species 

 which resemble each other more than they do any other species ; the species so col- 

 lected under one name are collectively called a Genus, the common name being the 

 generic name. Each species is then distinguished from the others of the same genus 

 by the addition of an adjective epithet or specific name. Every species has thus a bo- 

 tanical name of two words. In Latin, the language usually used for the purpose, the 

 first word is a substantive and designates the genus ; the second, an adjective, indi- 

 cates the species. 



181. The genera thus formed being still too numerous (above 6,000) for study with- 

 out further arrangement, they have been classed upon the same principles ; viz. genera 

 which resemble each other more than they do any other genera, have been collected 

 together into groups of a higher degree called Families or Natural Orders, to 

 each of which a common name has been given. This name is in Latin an adjective 

 plural, usually taken from the name of some one typical genus, generally the best known, 

 the first discovered, or the most marked (e.g. Ranunculacece from Ranunculus). This 

 is however for the purpose of study and comparison. To speak of a species, to refer 

 to it and identify it, all that is necessary is to give the generic and specific names. 



182. Natural Orders themselves (of which we reckon near 200) are often in the 

 same manner collected into Classes ; and where Orders contain a large number of 

 genera, or genera a large number of species, they require further classification. The 

 genera of an Order are then collected into minor groups called Tribes, the species of 

 a genus into Sections, and in a few cases this intermediate classification is carried still 

 further. The names of these several groups the most generally adopted are as follows, 

 beginning with the most comprehensive or highest : — 



Classes. Genera. 



Subclasses or Alliances. Subgenera. 



Natural Orders or Families. Sections. 



Suborders. Subsections. 



Tribes. Species. 



Subtribes. Yarieties. 

 Divisions. 

 Subdivisions. 



