ABOUT THE OAKS OF THE UNITED STATES. 391 
Tn the LEAVES, so extremely variable in form, certain types are generally recognized. It is not 
here the place to expatiate on these well-known topics; but I may be allowed the observation, that 
those oaks, which in the perfect state have deeply-lobed or pinnatifid leaves, show in young shoots 
or on adventitious branchlets less divided or only dentate, sinuate, or even entire leaves (e. g. Q. alba, 
stellata, falcata, coccinea, palustris, etc.), while, singularly enough, the oaks whose leaves in the adult 
tree are entire or nearly so, often have on the young shoots dentate or lobed leaves. I need, for 
examples, only refer to Q. aquatica, Q. Phellos, and Q. virens; and even Q. nigra belongs here. 
The vernation of the oak leaves has sometimes been mentioned as conduplicate, meaning that 
the upper sides of both halves of the nascent leaf are applied together, and this really is the case 
with most oaks which I have been able to examine in this early stage. We find it both in white 
and black oaks, — almost always, I believe, in those with broad and deeply-lobed leaves; I mention 
only @. alba, macrocarpa and Garryana, Q. coccinea and palustris, and also the forms allied to 
Q. Prinus, even those with narrower, dentate leaves. In the more deeply-lobed, broad-leaved black- 
oaks, the two halves of the leaf are, besides, plicate parallel with the principal nerves. 
Next to these range the oaks with the young leaves concave and imbricately cov- 
ering one another. Such we find in Q. stellata of the first, and Q. nigra of the second [876 (5)] 
group, both with densely tomentose, thick, young leaves. In other oaks, mostly such as 
have broader and more or less entire leaves, the young leaves imbricatively cover one another like 
those last mentioned, but are convex on the upper side, with the edges turned down or back. Such 
is the case in Q. cinerea, myrtifolia, agrifolia, aquatica, chrysolepis, and, I believe, also in Q. wndu- 
lata, and in Q. Wislizeni. I find the same to be the case in the deeply-lobed Q. falcata. 
The narrow-leaved oaks of both sections have revolute young leaves, the halves being spirally 
rolled backward towards the midrib, so that only the upper side of the leaf is exposed; the point of 
the young leaf is somewhat spreading so that the branchlet has a squarrose appearance, while in those 
with imbricative vernation it is compact. I find the revolute leaf in Q. virens, pumila, Phellos, hetero- 
phylla, and imbricaria. In Q. Catesbei I observe an inflexed vernation, the long bristle-pointed lobes 
of the nascent leaf being curved down over the still younger one. 
I believe that the characters of vernation will not only help to distinguish allied species or doubt- 
ful varieties, but will also assist in unravelling the intricate questions of hybridity. 
The young leaves of almost every oak are coated with a dense stellate down, which in some 
(Q. alba, rubra, ete.) is early deciduous, or it disappears later, or is entirely persistent. Besides these 
stellate one-celled hairs, several species, those with a clammy feeling of the young leaf, have another 
kind of hair, single or a few stellately connected, consisting of several cells, obtuse or clavate, some- 
times branched, and often colored, apparently glandular. I notice these articulate hairs, among the 
white-oaks, in Q. stellata, and less conspicuously in Q. macrocarpa ; among the black-oaks, in Q. nigra 
myrtifolia, cinerea, falcata, aquatica, and laurifolia ; in Q. chrysolepis the characteristic “ golden scales ” 
are no scales, but consist entirely of such articulated yellow hair, and the young Q. Catesbai has the 
same rusty coating. 
The venation and more or less distinct reticulation of the leaves also present characters not to be 
neglected; by them, e. g. two easily confounded Californian oaks, Q. agrifolia and Wislizeni, can 
readily be distinguished even in sterile branchlets. 
The persistence of the leaves is a good character in some species, while in others it is [377 (6)] 
unreliable ; Q. pumila and laurifolia on the eastern and Q. agrifolia on the western coast 
sometimes retain their leaves until the new ones are fully developed, and other specimens, even in 
the same neighborhood, lose them before the buds swell; some have deciduous leaves northward and 
partly persistent ones southward. The broad-leaved forms of Q. undulata are decidedly deciduous, 
while those with small, coriaceous, spiny-toothed leaves retain them through part of the winter, or, 
toward their southwestern limit, even into summer. Only such oaks ought to be called evergreen 
