COMPOSITION AND PURPOSES OF PLANTS 5 



flowers yellowisli-red, and appearing before the leaves 

 in the spring. The leaves show the most brilliant 

 colors in the autumn. This is the red maple (Acer 

 ruhrum), and the sugar maple and the red maple 

 trees each constitute a species. The trees of each 

 species live in certain kinds of places, and have 

 distinct forms of leaves, twigs, fruit, and flowers 

 adapted to the conditions under which they exist, 

 and these organs are developed at such season in 

 the two species as will enable each to do its w^ork 

 in the best manner. 



The violets are among the earliest spring flowers, 

 and it would be possible in a great many localities to 

 find some with white, others with blue, and others 

 with yellow flowers. Dig up a specimen of each and 

 lay them side by side on the table or a sheet of 

 paper. Compare the roots, stems, leaves, and flowers, 

 as to their number, where attached, form, and color. 



This will show that the three violets have developed 

 their organs in various manners, and that the three 

 are members of tliree different species of the violets. 



A good conception of the difference between spe- 

 cies may be gained from a comparison of a wild 

 cherry tree with those in any orchard, and of the 

 slippery elm with the white elm. 



