THE PLANT KINGDOM 259 



in the organization. In the taxonomy of the plant kingdom a 

 somewhat similar series of groups within groups has been 

 recognized and its parts named, precisely as in a military organi- 

 zation. The most important of these groups are the species, 

 genus, faintly, order, class and division, although additional 

 ones are often employed. Thus all the individuals which are 

 like one another are grouped together and constitute a species, 

 of which we may take the Dog Rose as an example. This 

 species is clearly very similar to a large number of other species, 

 the Prairie Rose, the Swamp Rose, the Sweetbriar and many 

 others. All of these species, which we presume have descended 

 from the same ancestors originally, are grouped together as the 

 Rose genus (plural, genera, Fig. 140), the scientific name for which 

 is Rosa; and each of the species also has a scientific name of its own, 

 which for the Dog Rosa is canina. From the general structure 

 of their flowers, fruit and other organs, we believe that this Rose 

 genus is closely related to other somewhat similar genera, such 

 as the Cherries {Prunus), the Apples (Malus), the Hawthorns 

 (Cra^aeg-Ms), the Blackberries (Ruhus), the Strawberries {Fragaria), 

 and others; and we therefore group all of these genera together 

 into a still larger unit, the family, which in this case is the Rose 

 family or Rosaceae. This is a large family, containing about 40 

 genera and 3,000 species. It is evidently similar in many respects 

 to certain other families, notably the Saxifrage family (Saxifraga- 

 ceae) and the Legume family (Leguminosae). This group of 

 families, which stand somewhat by themselves and are probably 

 all related to one another by descent, we call an order, in this 

 case the Rosales* The Rosales are one of a large number of 

 orders which constitute the great class of Dicotyledoneae or 

 dicotyledonous plants. This is clearly distinguished from 

 another great class, the Monocotyledoneae or monocotyledonous 

 plants; and these two classes comprise the subdivision which we 

 call the Angiospermae or angiosperms. The angiosperms, 

 together with the more ancient but now much smaller subdivision 

 Gymnospermae, or gymnosperms, make up the division known 

 as the Sprrmatophyta or seed plants, with which we have already 

 become acquainted as one of the four main groups into which 

 the plant kingdom is divided. 



* In generul, the scientific name of a family has tlie ending -ccac, tliat of 

 an order, -ales. 



