AMERICAN 
JOURNAL OF BOTANY 
Vol. VIII April, 1921 No. 4 
THE MORPHOLOGY AND ANATOMY OF RHUS DIVERSILOBA 
James B. McNair 
(Received for publication November 2, 1920) 
Rhus diversiloha T. & G. may be either a low deciduous shrub or a high 
dimbing vine as it readily adapts itself to local conditions. In sunny ex- 
posures it most frequently occurs as a low shrub 3 to 4 feet high. One 
instance is known, however, of a tree-like plant, 14 feet high with a diameter 
at its base of 6 inches. In shady locations it more frequently assumes a 
vine-like form and by means of its aerial rootlets ascends the trunks of 
trees to a height of 15 to 20 feet. 
The new wood has pale grayish bark, is light in weight, brittle, and 
contains much pith. The ends of the young shoots and the petioles are 
usually red-brown in color. In the early spring groups of plants may be 
distinguished at a distance before fully leafing out by this red-brown of the 
young stems and leaves. The branches gradually become woody with the 
accumulation of successive annual rings, the bark thickens, roughens, and 
becomes the abode of many lichens and mosses. The bark on the old wood 
is brown-gray, furrowed lengthwise, has horizontal rows of wart-like lenti- 
cels, and on dead limbs peels off laterally, not spirally. The large branches 
have but few small lateral branches. In its shrubby form no difference can 
be observed between the height of the male and that of the female plants, 
nor can any noticeable difference be determined in the angles which the 
branches subtend to the trunk. The leaflets, too, generally have similar 
shapes on both plants. 
Flower panicles do not develop on the ends of young shoots, but form 
on the sides. The apical bud makes a growth of 4 to 5 centimeters per 
year. It requires about four weeks for the full development of a leaf. 
The flower and leaf buds begin to expand simultaneously, but the leaves 
soon expand more rapidly and consequently some of the leaves reach 
maturity before the flowers open. The expanding leaves are very tender 
and turgid, and sap flows quickly out of injured stem or leaf areas. These 
leaves are arranged alternately on the stem and have a phyllotaxy of 8/21. 
The leaf scars are triangular in outline. The swelling where the leaf is 
attached may have the function, by its growth, of turning the leaf to a 
better exposure. 
[The Journal for March (8: 127-178) was issued April 3, 1921.] 
179 
