18 BULLETIN- 820, U. S. DEPAETMENT OF AGKICULTURE. 



ards A and B being for higher-growing species. In a letter review- 

 ing the manuscript on which this bulletin is based Prof. Filibert 

 Both says: 



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 Mchigan. 



It wiU be seen that the "good" site in Hubbard County is slightly 

 better than Roth's Site II, while the "poor" site is halfway between 

 Sites II and HI. 



REPRODUCTION. 



SEED KiODUCTION. 



eTack 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 extrem^ely important. As a matter of 

 fact, the fruitfuhiess of jack pine, combined with its abihty 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 Pis. IX and X.) 

 Jack pine, like lodgepole, is a "fire tree," quickly seeding up bare- 

 burned spots or areas. It seeds weU 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 a,nd 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 contain from one-fourth to one-half pound of seed, each cone 

 having from 25 to 50 seeds. ^ Very heavily loaded jack pines some- 

 times yield 1^ 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 pLae. 



