14. ~—- BULLETIN 460, U. S. DEPARTMENT OF AGRICULTURE. 
Mature cones are from 4? to 94 inches long (Pls. VII and IX). 
The most distinctive characteristic of the cone is the strongly reflexed 
thin tips of the cone scales. (Pl. VII, a, b.) No other pine in the 
United States has cones so strongly marked. The pendent cones are 
mature about the middle of September and usually drop their seeds. 
by the middle of October. They fall from the trees in late autumn — 
or early winter. At maturity the cones are light yellowish-brown, 
unexposed parts of the scales being dull red. The nutlike seeds are 
dark brown, slightly tinged with red, and are provided with a very 
short wing. (Pl. VII, c,d.) The seed-leaves are from 10 to 12 in 
number. (PI. IX, a.) 
The wood of Mexican white pine is moderately heavy fe a white 
pine, a cubic foot of it when dry weighing about 304 pounds. It is 
rather hard and narrow-ringed (“fine-grained ”1). The sapwood is 
thin and whitish, the heartwood being a very pale reddish-brown. 
In general appearance and texture lumber from this tree resembles 
that from old trees of the eastern white pine (Pinus strobus), while 
its “ working” qualities are similar to those of western white pine 
(Pinus monticola). The limited distribution of this tree in the 
United States and its occurrence in places difficult of access has so 
far prevented any but local use of the timber, the best grades of 
~ which would readily serve as a substitute for western white pine. 
OCCURRENCE AND HABITS. 
Mexican white pine grows in dry, rocky, or gravelly soils on moun- 
tain slopes, canyon sides, and ridges at elevations of from about 
5,500 to 9,700 feet; it is only very occasionally that straggling trees 
1 The popular conception of the “ grain’? of wood appears to refer mainly, if not en- 
tirely, to the thickness of the annual layers of growth. Thus wocds with thin or thick 
layers of growth are commonly called “‘ fine-grained ’’ or ‘* coarse-grained.’ Such other 
qualities of wood as compactness or density and porcsity of structure are popularly de- 
scribed as “ dense,’ ‘‘ very dense,’ ‘‘ compact,’ or es “‘ porous” and ‘‘ nonporous.” In 
view of this evident popular confusion in reference to “ grain,’ it is here maintained that 
grain should properly refer only to the structural corstitution of wood within the annual 
or other periodic layers of growth, and not to the thickness of the annual increment, 
which is consistently described by such terms as ‘“ wide-ringed’’ and ‘“‘ narrow-ringed ” 
wood. Uniform thickness of the periodic layer of srowth is only exceptionally character- 
istic of any wood under all conditions of the tree’s life, while the structural elements of 
different woods remain fairly constant. The characteristic structure of different woods 
results from the association of different individual cell-elements (fibers and vessels). 
These elements have distinctive forms, which vary within limits characteristic of dif- 
ferent groups of woods, and also of the same species grown under different conditions. 
Wood elements are also characteristically assembled in different genera and species of 
woods. In one, these elements may be so associated as to form the popular and correctly 
termed “ cross-grained ” wood, as in sycamore (Platanus) and in gum (Nyssa), etc. 
In another, they may form “ straight-grained’’ wood, as in white ash, white pine, etc. 
Again, the elements may take a wavy longitudinal course, or an abruptly-curved course, 
and produce the “ curly-grained”’ and ‘ bfrds-eye”’ wood. So aiso, when the elements 
are spirally disposed with reference to the axis of the tree, the wood has a “ twisted 
grain.” If all of the elements of a wood are small and about the same width, the struc- 
ture can properly be termed “fine-grained.” So, too, if many of the cell-elements are 
large, the wood produced is * coarse-grained,” 
