138 AMERICAN MIDLAND NATURALIST 
and at the ends of the twigs of preceding years growth; racemes 
on short side branches 1 cm or less in length, with or without 
reduced simple or ternate leaves; peduncles 2-2.5 cm. long: samaras 
densely clustered, in appearance usually smaller: samara wings 
joined usually at an acute angle at the base, and not at all, or not 
much attenuated; fruit body glabrous. 
From Rulac interior it is easily distinguished by its glaucous 
white twigs, those of the latter being minutely and retrorsely or 
spreading tomentulose. The leaves of R. interior are almost 
invariably trifoliolate and the three leaflets give the whole leaves 
a characteristic regular appearance wanting in the eastern and 
middle western plants. 
This seems to be the native midland Box-elder and extends 
from the western slopes of the Appalachian Mountain system to 
the foot-hills of the Rocky Mountains and north of the Ohio 
River and Missouri. "The tree seems to be more hardy than the 
eastern one, and has been found more often in cultivation. 
Specimens in the United States Herbarium show it to be 
found in the Eastern states, New York, California, Mexico, and 
cultivated in European gardens and parks. The eastern species 
seems almost totally absent from the Middle West. 
Rather typical plants are present in my herbarium as numbers 
675, 2165, 2174, 2175, 2168, 2169, from Notre Dame and vicinity. 
Mr. Deam’s collection from various parts of the State of Indiana 
contain some good examples. Some have rather attenuated fruit 
bases. The specimens in the U. S. National Herbarium as also 
in the New York Botanical Garden Herbarium are too numerous 
to give individual mention and reference, though I have a record 
of all to date. One specimen in Mr. Deam’s collection from Missouri 
has extremely narrowly angled fruit bases, and large wings that 
overlap each other. 
Rulac Nuttallii is readily distinguished by its thick irregu- 
larly dentate leaves, and glaucous twigs and petioles. The wings 
of R. interior are minutely tomentulose and the leaves though 
variously dentate are trifoliolate and the whole leaf has a very 
symmetrical appearance, taking the leaflets together. This is 
lacking in the irregularly leaved midland specimens, one-half 
of the terminal leaflet is hardly as symmetrical as the other, nor 
do the basal ones help in the symmetry of outline of the whole. 
The leaves of R. Nuttallii have oftener 5-11 leaflets than any 
