44 BULLETIN 460, U. S. DEPARTMENT OP AGRICULTURE. 



and those produced each year remain on the branches until about the 

 third summer ; in some instances, however, many of them die and fall 

 from the trees during the second season. They are usually curved, 

 and are borne in bundles of two (PL XXVIII, «, b). In length they 

 vary from about seven-eighths of an inch to nearly 1^ inches, but 

 commonly they are about an inch long. The edges of the leaves bear 

 minute and widely-separated teeth (serratures). A slightly mag- 

 nified cross section of the leaf shows, as a rule, two resin ducts, 

 one in each angle of the section (edge of leaf) ; occasional leaves ap- 

 pear to be without resin ducts. 



The characteristically one-sided cones (PI. XXVIII, b, c) are 

 fully mature by September of the second season, and two, three, or 

 four of them may be borne in one cluster. They vary in length 

 from 1| to about 2 inches and from one-half to nearly 1 inch in 

 diameter at the thickest place. Early in autumn they are a greenish 

 to a deep purple, but later they turn to a light clay-brown, the ends 

 of the closely pressed cone scales being shiny. During the first season 

 the scales of young cones bear delicate curved prickles, which, how- 

 ever, usually disappear or are very inconspicuous by the time the 

 cones are ripe. A characteristic habit of the cones of this pine is to 

 remain attached to the trees for from 12 to 25 years or more. The 

 cones are peculiar also in that they open irregularly and liberate 

 only a few of their seeds at a time and then usually only after the 

 cones have remained closed for two or three years. The triangular 

 seeds are from one-eighth to three- sixteenths of an inch long and 

 about three thirty-seconds of an inch wide, and are covered with a 

 blackish-brown minutely pebbled membrane, tiny bits of which 

 become detached and show the light yellow-brown shell of the seed 

 beneath. The upper side of the seed is more or less distinctly marked 

 with two grooves. The seed-leaves vary in number from four to 

 five (PI. XXVIII, e; lowermost long leaves). 



Jack pine wood is variable in texture and weight from rather soft 

 and light to rather hard and moderately heavy, some grades of the 

 wood being nearly of the same hardness and weight as Norway pine. 

 A cubic foot of dry wood weighs about 29f pounds. When seasoned 

 it is brittle and weak and decays rapidly in contact with earth. The 

 sapwood is thick and of a uniform pale creamy white, but the heart- 

 wood varies in color from a bright, slightly brownish yellow to a 

 light yellow-brown. The wood formed during the first 15 or 20 

 years, when the tree grows rapidly, is moderately wide-ringed; that 

 formed during the remainder of the tree's life, when diameter growth 

 is very much slower, is narrow-ringed — sometimes exceedingly so. 

 Little is known now regarding the use, if any, of this timber in the 

 far northwestern range of the tree. In the central and eastern parts 



