552 ACERACEAE 



same number, inserted on the margins of an indistinct disk, or very often 

 wanting. Stamens 4-9, often 8. Gynoecium of two united carpels; styles 

 united. Fruit of 2 winged carpels, united below (samaras). 

 Leaves palmately lobed or rarely palmatedly compound; flowers polygamous or perfect. 



1 AOKR 



Leaves pinnately compound; flowers dioecious. 2. Negundo. 



1. ACER (Tourn.) L. Maple. 



Trees or rarely shrubs. Leaves opposite, petioled, more or less palmately 

 lobed or cleft, rarely palmately compound. Flowers polj'gamous or rarely 

 perfect, regular, in axillary or terminal racemes or corymbs. Sepals 4 or 5, 

 rarely 6-9. Disk cup-shaped, lobed, or more commonly obsolete or wanting. 

 Stamens 4-9. Petals as many as the sepals or wanting. Samaras 2, with reticu- 

 late wings. 



Flowers in racemes or corymbs: petals and sepals both present; disk well developed: 

 lobes of the leaves toothed. 

 Flowers in long racemes, appearing after the leaves; leaves long-acuminate, with 



small lateral lobes; petals longer than the sepals. 1. A. spicatum. 



Flowers corymbose, appearing with the leaves; leaves not long-acuminate, deeply 

 3-5-cleft; terminal lobe only slightly larger; petals and sepals greenish, sub- 

 equal. 

 Bark of the one-year-old branches grajdsh; leaves and their lobes acuminate, not 

 dotted beneath. 

 Sinuses between the leaf-lobes shallow, open ; terminal lobe broadly triangular- 

 ovate. 2. A. Douglasii. 

 Sinuses between the leaf-lobes deep and narrow; terminal lobe rhombic. 



3. A. glabrum. 



Bark of the one-year-old branches white; leaves and their lobes acute, not acum- 

 inate, with more or less numerous glandular red dots beneath. 



4. A. triparlitum. 

 Flowers in umbels, appearing with the leaves; petals lacking; lobes of the leaves sinuate. 



5. A. grandidenlatum. 



1. A. spicatum Lam. Shrub or small tree, sometimes 10 m. high, with 

 thin smooth bark; twigs somewhat velutinous-puberulent or glabrate in age; 

 leaf-blades longer than broad, cordate, 3-lobed, glabrate above, paler and pubes- 

 cent beneath; petals linear or spatulate; samaras about 2 cm. long; wings ascend- 

 ing-spreading at about 90°; backs nearly straight. Rocky woods and mountain 

 slopes: Xe%\'f. — Ga. — Minn. — Sask. Boreal. My-Je. 



2. A. Douglasii Hook. Shrub or small tree, sometimes 10 m. high; twigs 

 glabrous, purplish or red; older branches grayish; leaf -blades broadly cordate in 

 outline, 3-10 cm. long and about as broad, 3-5-Iobed, or on young shoots and 

 vigorous twigs sometimes 3-divided to the base, glabrous on both sides; samaras 

 3-4 cm. long, ascending, usually incurved on the back; sinus usually rounded. 

 A. subserratum Greene. Hills and mountain sides: Alta.— Wyo. — Ore. — B.C. 

 Submont. — Mont. Ap-Je. 



3. A. glabrum Torrey. Usually a small tree, 5-15 m. high; twigs glabrous, 

 reddish; older branches gray; leaf -blades broadly cordate or roundcd-reniform 

 in outline, 4-8 cm. long, 4-10 cm. wide, glabrous, 5-7 lobed, or usually on young 

 shoots and vigorous branches or sometimes on the whole tree 3-divided to the 

 base; samaras 2.5-3 cm. long, usually straight on the back; sinus usually acute. 

 A. neomexicanum Greene. Mountains, usually along streams: S.D. — N.M. — 

 Utah — Wyo. Submont. — Mont. My-Je. 



4. A. tripartitum Nutt. Shrub 1-5 m. high; twigs reddish, glabrous; 

 leaf-blades rounded-reniform in outline, glabrous above, more or less puberulent 

 beneath, shining, 3-5-lobed or -cleft or sometimes [as in the type specimens] 3- 

 parted to the base, the terminal lobe more or less rhf)mbic, coarsely toothed, 

 2-4 cm. long, 2-5 cm. wide; samaras 2-2.5 cm. long, a.scending, incurved on the 

 back, forming with each other a narrow angle. Dry hills: Wyo. — Utah — s 

 Calif. Son. — Submont. My-Je. 



5. A. grandidentatum Nutt. Shrub or rarely a small tree, 5 m. high, 

 with light brown twigs and gray branches; leaves reniform or orbicular in out- 

 line, deeply 3-5 lobed, with rounded sinuses, glabrous, pale and velutinous 



