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THE MAPLE FAMILY— ACERACEAE. 

 The Maple family comprises in addition to the Asiatic genus Dip- 

 teronia, with only 1 species, about 70 species, all of which are in- 

 cluded in the genus Acer, and distributed with a few exceptions in 

 the northern hemisphere. This family consists mainly of trees and 

 a few shrubs. The members of this family are used more than those 

 of any other family as ornamental and shade trees. Further charac- 

 teristics of the family are included in the description of the sole 

 American genus which follows. 



THE MAPLES— ACER, (Tourn.) L. 



This genus comprises approximately 70 species in the world, with 

 13 species in the United States and 6 species in Pennsylvania. A 

 few exotic species have been introduced exclusively for ornamental 

 and shade purposes. The commonest exotic species are the Norway 

 Maple (Acer platanoides L.) and the Sycamore Maple (Acer Pseudo- 

 platanus L.). On account of their abundance and wide distribution 

 in this State, a descriptive page, together with an accompanying 

 plate, has been devoted to these two species. 



The leaves of the Maples are opposite, usually simple or in a few 

 species compound with 3-5 leaflets, and are shed in the autumn. The 

 flowers are regular or polygamous, rarely perfect, and appear before, 

 with or after the leaves. The time at which the flowers appear aids 

 considerably in distinguishing the various species from each other. 

 Some trees bear only staminate flowers, while others bear only pis- 

 tillate, with the result that one may occasionally find a mature tree 

 which does not produce any fruit. The flowers are pollinated by in- 

 sects, which are attracted in hordes by the aromatic pollen-bearing 

 blossoms. The fruit is composed of a pair of winged seeds joined to- 

 gether to form the well-known maple key or samara, which matures 

 in early or late summer, depending upon the species. The fruit 

 which matures in early summer germinates at once, while that which 

 matures in late summer remains dormant over winter and germinates 

 the following spring. Wind is the chief agent which disseminates 

 the seeds. 



The Maples are separated into two classes with reference to their 

 commercial value. Hard Maple and Soft Maple. This classification 

 is based upon the physical characteristics of the wood. The wood 

 of the Maple is diffuse-porous with rather small medullary rays, 

 usually fine-grained, dense, and in some species hard and beautifully 

 curled and figured, which makes it especially prized for interior 

 finish and cabinet work. Most species yield a saccharine sap which 

 may be concentrated into maple syrup or maple sugar. 



Within a family one may often find a wide variation of plant or- 

 gans, but the genus Acer possibly presents a wider range or a greater 



