20 ENGELMANN-OAKS OF THE UNITED STATES. [39 r ^ 
Jg. olivceformis , Michx., is, according to A. Gray, a variety of 
macrocarpa. After carefully comparing several specimens refer* 
red to olivceformis with numerous forms of macrocarpa, I cannot 
but fully coincide with this view. Mr. E. Hall of Menard Co., 
Ills., has a found a tree in his neighborhood which has exactly 
the leaves of olivceformis , as figured by Michaux, lobed so deeply 
that the midrib is nearly bare, with an ovate fruit larger than that 
of Michaux (which was most probably incomplete or abortive), 
and about half immersed in the deep, not fringed, strongly knob¬ 
bed cup. This specimen has been claimed as a hybrid of macro - 
carpa and alba (Amer. Ent. & Bot. 1870, p. 191). Such leaves, 
however, are not very rare in macrocarp a, and I have repeatedly 
seen in western forms of macrocarpa exactly the same kind of 
acorns, with or without a fringe on the edge of the cup. 
jg. runcinata was the name given to a form I found in the 
richest Mississippi-bottom lands opposite St. Louis, together with 
rubra , imbricaria , and palustris. From its smaller and nar¬ 
rower, grossly dentate, not lobed leaves, and its smaller fruit, it 
seemed distinct enough from rubra , and was possibly a hybrid 
of it and some other small-fruited allied oak. But the leaves of 
rubra are so variable in size and outline that most probably 
DeCandolle ( 1 . c. 60) is right in considering it a variety of rubra. 
Q. quinqueloba I named a form of nigra with 5-lobed leaves, 
which I found on the hills of St. Louis ; DeCandolle ( 1 . c. 64) 
places it correctly with nigra. It is not even a variety, but ra¬ 
ther a juvenile state which had become permanent in that tree; 
young trees or shoots of nigra have sinuate-dentate or many- 
lobed leaves, but in fertile ones the leaves are almost always 
more or less 3-lobed or 3-dentate. I have since seen a tree which 
on one fruit-bearing branch had only the leaves of quinqueloba , 
while all the other branches had the regular cuneate 3-dentate 
nigra leaves. 
heterophylla , Michx., has by some been considered a hy¬ 
brid of some species with entire, narrow leaves, and a lobed one ; 
DeCandolle takes it for a form of aquatica , and Gray partly for 
that, partly for a form of Pkellos. I have above expressed my 
opinion that it is a good species, not to be confounded with the 
lobe- leaved forms of either. 
Missouri Botanical Garden 
George Engelmann Papers 
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