ACER 
Acer, Linneus, Sp. Pl. 1054 (1753); Bentham et Hooker, Gen. Fi. i. 409 (1862); Pax, in Engler, 
Phlanzenreich, iv. 163, Aceracee, 6 (1902); Schneider, Laubholzkunde, ii. 192 (1907). 
Negundo, Ludwig, Gen. Pl. 308 (1760); Bentham et Hooker, oc. cet. 
Trees or shrubs, belonging to the natural order Aceracez, which is often 
considered to be a division of Sapindacee. Leaves usually deciduous, rarely 
evergreen, opposite, without stipules—simple, in which case they are undivided 
or palmately lobed—or compound with three to five leaflets. Buds covered by 
several scales arranged in decussate pairs, or protected by two valvate scales, 
sessile or occasionally stalked. Twigs with epidermis persisting for more than 
one year and remaining green in the second year; or becoming corky on the 
surface and changing colour in the first season. Inflorescence terminal on two- 
to four-leaved branchlets, or arising out of lateral buds without leaves, in racemes, 
corymbs, or fascicles. Flowers appearing at the same time as the leaves or earlier ; 
regular, dicecious, or with male and perfect flowers on the same tree, or with male 
flowers on one tree and perfect flowers on another tree. Parts of the flowers in 
fours or fives or multiples of those numbers. Calyx with four, five, to twelve sepals, 
usually free, occasionally connate. Petals equal in number to the sepals, absent 
in some species. Disc secreting honey usually present, absent in a few species, 
annular, lobed, or reduced to small teeth. Stamens four to ten, usually eight, 
inserted either outside the disc, inside it, or upon it. Ovary, two-lobed, two- 
celled, each cell containing two ovules. Styles or stigmas two, free or connate 
at the base. Fruit of two samara, attached by their bases, with long and 
diverging wings. Seeds one or two in each samara, without albumen; cotyledons 
appearing above the ground on germination. 
About 110 species of maple are known, occurring usually in mountainous 
regions; in Europe, south of lat. 62°, in Algeria, Asia Minor, the Caucasus, 
Persia, Turkestan, the Himalayas, China, Manchuria, Japan, Formosa, the 
Philippines, Java, Sumatra, Celebes, and in North America from Southern 
Canada and Oregon to Mexico and Guatemala. A large number have been 
introduced into cultivation, fifty-seven species being enumerated in the Kew 
Hand-List; but many of these are shrubs or small trees, the detailed treatment 
of which does not come within the scope of our work. 
The genus is divided by natural characters into thirteen sections by Pax, 
whose monograph and that of Schneider should be consulted by cultivators of the 
630 
