180 TREES AND TREE-PLANTING. 
oak is given by Dr. P. R. Hoy, of Racine, an accom- 
plished naturalist, and member of the Philadelphia 
Academy of Natural Sciences: “This is, perhaps, the 
most ornamental of our oaks. Nothing can exceed the 
graceful beauty of these trees when not crowded or 
cramped in their growth, but left free to follow the laws 
of their development. Who has not admired these trees 
in our extensive burr-oak openings? Its large leaves 
are a dark green above and a bright silvery white be- 
neath, which gives the tree a singularly fine appearance 
when agitated by the wind. The wood is tough, close- 
grained, and more durable than the white oak, especially 
when exposed to frequent changes of moisture and dry- 
ness. Did the tree grow to the same size it would be 
preferred for most uses. Abundant and richly worthy 
of cultivation, both for utility and ornament, burr oaks 
in Wisconsin do not generally attain more than one foot 
in diameter, and the limbs grow near the ground, mak- 
ing a sort of espalier, and rarely growing higher than 
thirty to forty feet, straight, with very rough bark. 
The acorn is enclosed in a burr something like a chest- 
nut, hence their name.” 
This is the most useful of all trees. Loudon describes 
somewhere in the neighborhood of one hundred and 
twenty, and this number has since been added to. These 
trees are found mostly in the temperate zone; those that 
we find in the tropics are in elevated positions. It 
is found distributed over Europe and North America. 
These trees are of a beautiful appearance, and have not 
been paid sufficient attention as ornamental trees. Bry- 
ant says: “In many of the oaks the form of the leaves 
varies so much with different conditions of the tree, or 
different stages of its growth, that it constitutes an un- 
certain characteristic by which to distinguish the species. 
Consequently, where the wood is similar, different spe- 
cies are sometimes confounded under one name. The 
fructification affords a more certain mode of distinction.” 
