18 BULLETIN 820, U. S. DEPARTMENT OF AGRICULTURE. 
ards A and B being for higher-growing species. In a letter review- 
ing the manuscript on which this bulletin is based Prof. Filibert 
Roth says: 3 
I recommend that this standard of 90, 75, 60, and 45 feet for I, II, III, and IV sites 
be made a regularly accepted or adopted standard and called standard C, and that 
all species in the United States which have a growth near to jack pine have their 
sites established and measured by this same standard C site classification on the basis 
of height at 100 years, with values as given in figure 3, which works out well with 
data here gathered. 
Site I in older stands is represented sparingly in these studies (referring to the 
manuscript), because in Minnesota jack pine does not get a chance on Site I, since 
these run to Norway pine. 
Site IV is also little represented, but is abundant in Wisconsin and Michigan. 
Tt will be seen that the “good” site in Hubbard County is slightly 
better than Roth’s Site I, while the “‘poor”’ site is halfway between 
Sites IT and HI. 
REPRODUCTION, 
SEED PRODUCTION. 
Jgack pine produces a great quantity of seed. In view of the com- 
parative shortness of the life of jack pine and its intolerance of 
shade, this characteristic is extremely important. As a matter of 
fact, the fruitfulness of jack pine, combined with its ability to grow 
on soils too poor, at the outset, for other species, is the means by 
which it is able to maintain itself as one of the most widespread 
and important forest types of the North. (See Pls. IX and X.) 
Jack pine, like lodgepole, is a “fire tree,” quickly seeding up bare- 
burned spots or areas. It seeds well almost every year and heavily 
every two or three years, in contrast with Norway and white pines, 
which do not seed every year and which seed in abundance only at 
intervals of from five to seven years and three to five years, respec- 
tively. Trees in the open or with abundant growing space are the 
most prolific seeders and commence to bear seed when from 6 to 8 
years old. Vigorous seed production continues up to 80 years of 
age, but is most vigorous between 40 and 80 years. 
A well-developed, vigorous tree produces from 1,000 to 1,200 
cones in a year, or from one-fourth to one-half bushel, and these 
cones contgin from one-fourth to one-half pound of seed, each cone 
having from 25 to 50 seeds. Very heavily loaded jack pmes some- 
times yield 14 bushels of cones. There are from 75,000 to 100,000 
seed per bushel of cones, and from 100,000 to 150,000 seed per pound. 
The cone matures the second year. The seed is ripe about Septem- 
ber 1 and dissemination commences soon afterwards. During dry 
seasons Many more cones open up than in wet. Nearly half of them 
1 Report of Cloquet, Minn. Experiment Station, October, 1917, gives an average of 30 jack pine seed 
per cone as compared with 37 seeds per cone in Norway pine. 
