660 TREES OF NORTH AMERICA 



4. RHUS L. 



Trees or shrubs, with pithy branchlets, fleshy roots, and milky sometimes caustic or 

 watery juice. Leaves unequally pinnate, or rarely simple. Flowers mostly dioecious, 

 rarely polygamous, white or greenish white, in more or less compound axillary or terminal 

 panicles, the staminate and pistillate usually produced on separate plants; calyx-lobes 

 united at base only, generally persistent; disk surrounding the base of the free ovary, co- 

 herent with the base of the calyx; petals longer than the calyx-lobes, inserted under the 

 margin of the disk, opposite its lobes, deciduous; stamens 5, inserted on the margin of the 

 disk alternate with the petals; filaments longer than the anthers; ovary ovoid or subglo- 

 bose, sessile; styles 3, terminal, free or slightly connate at base, rising from the centre of 

 the ovary. Fruit usually globose, smooth or covered with hairs; outer coat thin and 

 dry, more or less resinous; stone crustaceous or bony. Seed ovoid or reniform, commonly 

 transverse; cotyledons foliaceous, generally transverse; radicle long, uncinate, laterally 

 accumbent. 



Rhus is widely distributed, with more than one hundred species, in the extra-tropical 

 regions of the northern and southern hemispheres. In North America the genus is widely 

 and generally distributed from Canada to southern Mexico and from the shores of the 

 Atlantic to those of the Pacific Ocean, with sixteen or seventeen species within the territory 

 of the United States. Of these, four obtain the habit of small trees. The acrid poisonous 

 juice of Rhus vernicifera DC., of China, furnishes the black varnish used in China and 

 Japan in the manufacture of lacquer, and other species are valued for the tannin con- 

 tained in their leaves or for the wax obtained from their fruit. 



The name of the genus is from 'PoOs, the classical name of the European Sumach. 



CONSPECTUS OF NORTH AMERICAN ARBORESCENT SPECIES. 



Flowers in terminal thyrsoid panicles; fruit globular, clothed with acrid hairs; leaves un- 

 equally pinnate, deciduous; SUMACHS. 



Branches and leaf-stalks densely velvety hairy; leaflets 11-31, pale on the lower surface; 



fruit covered with long hairs; buds inclosed in the enlarged base of the petioles; 



juice milky. 1. R. typhina (A, C). 



Branches and leaf-stalks pubescent; rachis winged; leaflets 9-21, green on the lower 



surface; fruit pilose; buds not inclosed by the petioles; juice watery. 



2. R. copallina (A, C). 



Flowers in axillary slender panicles; fruit glabrous, white; leaves unequally pinnate, de- 

 ciduous; leaflets 7-13. 3. R. vernix (A, C). 

 Flowers in short compact terminal panicled racemes; fruit pubescent; leaves ovate, entire 

 or serrate, simple or rarely trifoliolate, persistent. 4. R. integrifolia (G). 



1. Rhus typhina L. Staghorn Sumach. 

 Rhus kirta Sudw. 



Leaves 16'-24' long, with a stout petiole usually red on the upper side and covered with 

 soft pale hairs, enlarged at base and surrounding and inclosing the bud developed in its 

 axil, and 11-31 oblong often falcate rather remotely and sharply serrate or rarely laciniate 

 long-pointed nearly sessile or short-stalked leaflets rounded or slightly heart-shaped at 

 base, covered above like the petiole and young shoots w r hen they first appear w r ith red 

 caducous hairs, bright yellow-green until half grown, and at maturity dark green and 

 rather opaque on the upper surface, pale or often nearly white on the. lower surface, glabrous 

 with the exception of the short fine hairs on the under side of the stout midrib, and primary 

 veins forked near the margins, opposite, or the lower leaflets slightly alternate, those of 

 the 3 or 4 middle pairs considerably longer than those at the ends of the leaf, 2'-5' long, 

 and I'-lV wide; turning in the autumn before falling bright scarlet with shades of crimsoa 



