10 PRINCIPLES OF PLANT CULTURE 



we may say that the different kinds of plants or animals 

 are called species. But these simple distinctions are not 

 sufficient to satisfy the needs of natural history. We 

 might say, for example, that the violet is one kind of 

 plant and the oak is another, which is true ; but there are 

 also different kinds of violets and different kinds of oaks. 

 We might say that the apple is one kind of plant and the 

 pear is another, but there are different kinds of apples, as 

 the crab apple and the common apple, and there are differ- 

 ent kinds of crab apples, and of common apples. We 

 must not only arrange the kinds of plants into groups, 

 but we must have groups of different grades. For ex- 

 ample, botanists call each distinct kind of plant, as the 

 sugar maple, the white oak and the dandelion, a species. 

 Then the species that rather closely resemble each other 

 are formed into groups, each of which is called a genus 

 (plural, genera), as the sugar maple and the soft maple; 

 the white oak, the red oak and the bur oak ; the raspberry 

 and the blackberry; and the apple, pear and quince. 

 Then the genera that resemble each other, as the one 

 containing the apple, pear and quince, and the one con- 

 taining the plum, cherry and peach, are formed into other 

 groups called families or orders. Thus families are made 

 up of genera, and genera are made up of species. There 

 may be, also, different varieties in the same species, as 

 the different varieties of apple, pea or strawberry. 



An extensive retail bookstore furnishes an object lesson 

 in classification, though we must remember that in natural 

 history it is usually the names and descriptions of plants 

 and animals that are classified, and not the plants and 

 animals themselves. In the bookstore, we will observe 

 that the books are not placed upon the shelves without 

 order, but that they are arranged in groups. Different 



