KEPBODTTCTTON OF WESTERN YELLOW PINE. 11 



crop, because of the extraordinary moisture conditions in 1919, will 

 yield much higher returns, possibly as high as 5 per cent and prob- 

 ably not less than 1 per cent. This should result in complete restock- 

 ing on areas which were well seeded. Heavy crops may fail to give 

 results, because they are not followed by suitable climatic conditions, 

 and likewise a period of favorable climatic conditions may be wholly 

 or partly ineffective, because it was not preceded by a good seed 

 crop. Although the right combination, such as was experienced in 

 1918 and 1919. appears to be purely a matter of chance, we should 

 aim to take advantage of such opportunities whenever they come. 

 The minimum seed supply, therefore, should be the amount required 

 to stock an area completely in one year under favorable climatic 

 conditions. Using experience in broadcast sowing in this country 

 and in Europe as a guide, and considering the many adverse condi- 

 tions encountered in this region, we may fix this amount somewhat 

 arbitrarily at 8 pounds per acre. 



NUMBER OF SEED TREES REQUIRED. 



The next question is, Hoav many trees per acre are needed to pro- 

 duce the required minimum amount of seed? Because of the great 

 variation in yield of different trees and the fluctuations from year 

 to year, it is difficult to answer this question satisfactorily. Esti- 

 mates should be based upon yield in good seed years. 



YIELD OF SEED IX VIRGIN STANDS. 



Table 5 shows the average yield and germination of seed from 

 trees of various sizes and descriptions in virgin stands for 1909 and 

 1913. Both of these seed crops were classed as "good." Unfor- 

 tunately the influenza epidemic in 1918 prevented securing data 

 from the heavy crop of that year. Estimates based upon a few trees, 

 however, indicate that the production was two or three times that of 

 an average " good " seed crop. Within the area of the heavy seed 

 crop in 1918, the yields are estimated to range from 15 pounds per 

 acre on Forest Service cutting to as high as 30 pounds in virgin 

 stands. In all collecting operations the cones were gathered from 

 trees felled in logging. Since the cones usually begin to open 

 within 10 days from the time the seeds are mature enough to col- 

 lect, considerable difficulty has been experienced in securing seed 

 from a sufficient number of trees to form a reliable basis for com- 

 parison. This applies particularly to blackjack, 4 because, being im- 

 mature, these trees form a small proportion of the total cut in a 

 logging operation on National Forest lands. One hundred trees 

 were represented in each of the 1909 and 1913 collections. 



4 " Pdackjaek " is a name locally applied to immature, dark-barked trees. The older, 

 yellow-barked trees are called "yellow pine." 



