82 



BULLETIN 139, U. S. DEPARTMENT OF AGRICULTURE. 



ment Station, in Minnesota. Two methods of seed collecting have 

 been tried out at the experiment station. One was to follow the 

 logging crew and gather the cones as the trees were felled. The 

 other was to collect the cones from squirrel hordes. The latter 

 method was found to be by far the best. Thus, when collecting the 

 cones from felled trees from 1 to 2 bushels was the average per man 

 per day; from 1 to 4 bushels was the average collected from squirrel 

 hordes. The largest caches of Norway pine found contained 1 

 bushel, while caches consisting of jack pine and Norway pine cones 

 often held 2 bushels. The average number of seed from cones was 

 found, to be 37, of which 23 were good and 14 bad. 



In general it was found that temperatures from 130° to 140° were 

 the ones at which the seed could be extracted easiest with the highest 

 percentage of germination. While for all temperatures used in the 

 test the mean per cent of germination was 70.8, for 130° to 140° the 

 per cent was 78.5. The lower germination per cent for tempera- 

 tures of less than 130° is accounted for by the fact that at that 

 temperature only the smaller and less fertile seed are released. In 

 Table 17 is given the length of time necessary for Norway pine to 

 crack and open at different temperatures. 



Table 17. — Length of time necessary for Norivay pine cones to crack and open at different 



temperatures. 



Tempera- 

 ture. 



Cracking. 



General 

 opening. 



Not open. 



o 



H. m. 



H. m. 



Per cent. 



125 



1 20 



4 35 



12 



130 



1 15 



4 15 



14 



135 



1 30 



4 



14 



140 



45 



3 45 



8 



145 



40 



2 30 



8 



150 



40 



2 22 



4 



155 



50 



2 25 



6 



160 



45 



2 30 



2 



165 

 170 



40 

 35 



2 15 

 2 20 





2 



175 

 200 



15 

 15 



2 

 1 30 









SOWING. 



Sowing is best done when the ground is free from weeds after log- 

 ging. If the seed average,s 55,000 to the pound, with a germinating 

 per cent of 90, broadcasting would require about 5 pounds per acre. 

 With the seed costing $4.50 a pound, sowing broadcast under these 

 circumstances would be absolutely prohibitive. In any event, broad- 

 casting will rarely be successful unless the soil is harrowed and raked 

 clear of weeds, though this would not be necessary on soil cleared 

 by fire directly after logging. It may often be practicable to sup- 

 plement natural regeneration by broadcasting on a soil bared by 

 logging when there is no seed crop. 



