xix THE CLASSIFICATION OF PLANTS 245 



Sub-Class .... Incomplete. 

 Natural Order. Distinguishing Characteristics. 



(a) Cupuliferae 



(i) Male flowers in catkins, 

 (ii) Female flowers sessile in an involucre of 

 bracts. 



Sub-Kingdom . . PHANEROGAMS. 

 Division .... ANGIOSPERMS. 



Class MONOCOTYLEDONS. 



Sub-Class .... Petaloideae. 



Natural Order. Distinguishing Characteristics. 



(a) Liliacese ... (i) Perianth either gamophyllous or poly- 



phyllous. 



(ii) Ovary superior ; ovules axile placentation. 



(b) Amaryllideae . . ! (i) Perianth generally with a corona (p. 281). 



I (ii) Ovary inferior. 



Meaning of a Natural Order. A natural order is built 

 up of a number of genera, each possessing some common charac- 

 ters. The genus in its turn includes several plants resembling 

 each other in one or more respects. The narrowest systematic 

 conception is the species. A species includes plants so closely 

 related that they must have descended from a common an- 

 cestor. 



Naming of Plants. Each plant receives two scientific 

 names ; the first indicates the genus, the second the species. 

 Thus, for instance, the Tormentil, Potentilla tormentilla, and 

 the silver-weed, Potentilla anserina, are two species of the 

 genus Potentilla. 



The following scheme indicates how each plant is arranged 

 in its true position in the natural system of classification ; 



Sub-Kingdom . . PHANEROGAMS. 



Division ANGIOSPERMS. 



Clans DICOTYLEDONS. 



Sub-Class ... Calyciflorse. 

 Natural Order . . Rosaceae. 



Genus Potentilla. 



Species Tormentilla or Anserina. 



