122 WOODY PLANTS OF MASSACHUSETTS. 
although, in the several species of the same group, there is a 
striking similarity, and I have gathered from the same stock, 
leaves which would seem to belong to several different species. 
Indeed, the nearly allied species are not to be distinguished by 
their leaves alone, viewed at any one season. 
The oak is distinguished from all other trees by its acorn, for 
which the fruit of no other treecan be mistaken. The leaves of 
all the species are larger towards the extreme end; in some, they 
are more or less deeply lobed, with rounded or blunt lobes; in 
others, toothed with large, round teeth; in others, deeply cut, 
with the divisions terminating in a long, bristle-like point, called 
a mucro. All the leaves are more or less downy while young, 
and many retain the down on the lower surface, when mature. 
The leaves of young plants, and of sprouts from the stumps of 
trees, are usually much more entire, as well as larger, than 
those on the mature tree. They come out late, and with them, 
or just before, the flowers. These differ less than the fruit, by 
which alone can some of the species be satisfactomly distin- 
guished. 
The stipules are membranaceous and perishing. The oak 
has but little medulla, but it continues in very old trees. 
The flowers of both sexes are on one plant; the sterile disposed 
in long, slender, pendulous catkins, which are in groups; the fer- 
tile flowers in a bud-like, scaly cup. The ovary or seed-vessel 
of the fertile flower is divided into three compartments or cells, 
in each of which are two embryo seeds or ovules; but only 
one ovule in one of the cells comes to perfection; hence the 
fruit is a one-celled, one-seeded acorn, surrounded at base by 
the enlarged, scaly cup. 
The acorns of the different species differ in being long and 
narrow, or short and round, pointed or blunt, on footstalks or 
sessile, and particularly in the scales of the cup in which the 
acorn is set. ‘The acorns of some species come to maturity in 
a single season, but a considerable part of the New England 
species require two seasons to ripen. There is scarcely any 
seed in which the vitality is so transient, at least when the acorn 
is preserved artificially. Few of them will germinate after 
having been kept a year. Most of the oaks, those particularly 
