Classification of Plants. 



361 



seeds or asexual propagative bodies, such as tubers, 

 rhizomes, etc., of the same parent plant, or from different 

 plants which in their turn sprang from a common parent, 

 and so on back for an indefinite number of generations. 

 Deviations from the type of the species which originate 

 when seeds from the same pod, for instance, or buds from 

 a common stock, are germinated and grown under different 

 conditions of soil or cli- 

 mate, are called varieties. 

 Our different kinds of 

 cultivated apples and po- 

 tatoes are good exam- 

 ples. Varieties which 

 tend to come true from 

 seeds are called races. 

 Then those groups of 

 species which are suffi- 

 ciently alike to indicate 

 a common ancestry at 

 some time in their his- 

 tory are classed under 

 one genus (plural, gen- 

 era\ and the groups of 

 genera of evident rela- 

 tionship are classed under a common order, or family, and 

 so on. 



We may find good illustrations of what has just been 

 said in the different kinds of wild raspberries and black- 

 berries. The high bush blackberry, Rubus villosus (Fig. 

 194), is a shrub with erect or recurved stems from three 

 to four feet long, having stout recurved prickles ; the leaf- 

 lets of the three to five foKate leaves are ovate oblong, with 

 margins closely serrate and with sharp points, and they 



Fig. 194. 

 Rubus villosus. After Britton and BROWN. 



