58 ELEMENTS OF STRUCTURAL BOTANY. 



The Ked Maple ripens its seeds early in the summer, 

 and these, on falling, germinate immediately, so that by the 

 autumn of the same year a vigorous young tree, a foot or 

 more in height, is produced. The seeds will not germi- 

 nate if kept over till the following spring. 



The Sugar Maple, on the other hand, flowers later, the 

 leaves and flowers appearing about the same time, and 

 the seeds do not ripen till the fall. If kept slightly moist 

 through the winter they will germinate the following 

 spring. 



76. The several species of common occurrence should 

 be carefully studied and distinguished. Their character- 

 istics are given in the proper place in Part II. 



The Maples form a subordinate group of the natural 

 Order Sapindacece. They are distinguished by the follow- 

 ing characters : 



1. The flowers are dioecious (orpolygamo-dicecious), and 



commonly unsymmetrical. 



2. The ovary is tioo-lobed and two-celled, with two 



ovules in each cell, only one of which, however^ is 



8. The fruit is a double samara. 



4. The leaves are opposite. 



77. From this type there are important deviations in 

 other representatives of the Order. Horse-chestnut, for 

 instance, while its flowers are unsymmetrical and some- 

 what irregular, as in the Maples, produces a three-celled 

 ovary, with two ovules in each cell. But as in Maple, 

 again, only one ovule in each cell forms a seed. The fruit, 

 however, is not a samara, but a leathery pod which splits 

 into three pieces at maturity, liberating the three large 

 shining seeds. 



