239 



all diseases and insect injury. The leaves appear late but they do not 

 fall until the first killing frost when they are killed, and frequently 

 practically all of "the leaves will fall in one day. The staminate flowers 

 exhale a fetid odor for a few days which is about the only objectionable 

 feature in this tree. In order to obviate this objection, nurserymen are 

 now offering for sale pistillate trees which have been grafted on com- 

 mon stock. 



ACERACEAE. THE MAPLE FAMILY. 

 ACER. THE MAPLES. 



Trees with terete branches; scaly buds; long petioled, opposite 

 leaves; fruit consists of two long-winged samaras which are joined at 

 their base, separating at maturity. The sap of some of the species, 

 when concentrated, yields the maple sugar and sirup of commerce. 



Leaves trifoliate or pinnate 1 A. Negundo. 



Leaves simple. 



Winter buds blunt; flowers appear from lateral buds before 



the leaves; fruit maturing in the spring or early summer. 



Leaves entirely glabrous beneath at maturity, 5-lobed; the 



two sinuses between the three largest lobes generally 



somewhat closed, formed as it were by the arcs of two 



circles which meet to form the sinus, and which if 



they were extended outward would cross each other 



within a few dm. of the sinus; fruit more or less 



pubescent at maturity 2 A. saccharinum . 



Leaves are never all entirely glabrous at maturity, 3-5 



lobed; the two largest sinuses are generally angular 



with straight sides which if extended outward would 



never cross; fruit smooth at maturity. 



Twigs smooth at maturity; leaves at maturity smooth 



beneath except a few hairs in the axils of the veins, 



or more rarely the entire lower surface covered 



more or less with a short pubescence; mature fruit 



generally 2-3.5 cm. long 3 A. rubrum. 



Twigs more or less pubescent at maturity; leaves 

 beneath covered with a dense tomentum which 

 remains until maturity or sometimes becoming 



scanty; fruit about 4-5 cm. long var. Drummondii. 



Winter buds acute, sometimes somewhat blunt; flowers 

 appear from terminal buds after the leaves ; fruit matur- 

 ing in the autumn. 



Leaves yellow green beneath; base of the petiole of the 

 terminal leaves enlarged at the base, smooth or 

 somewhat pubescent about the enlarged base 4 A. nigrum. 



