EFFECT OF FERTILIZATION ON THE SEED OF 



JEFFREY PINE 



E. N. MUNNS 

 Forest Examiner, United States Forest Service 



In May, 1914, the Jeffrey pine (Pinus jeffreyi) in the San 

 Bernardino Mountains of Southern California gave promise of a 

 forthcoming seed year, and when this was realized, plans were 

 made to determine the effect of the parents on the seed. To 

 this end, muslin sacks were tied around some of the pistillate 

 flowers on a number of trees; and when the pollen began to be 

 liberated, it was collected in envelopes from the various chosen 

 trees and the flowers were pollinated by the blowing of this 

 pollen onto the cones, care being taken that all portions of 

 the cones were thoroughly dusted. This pollination was done 

 three times at intervals of four days to make sure that all of the 

 flowers were covered, even those that were latest in becoming 

 receptive. When the pollen had ceased flying, the bags were 

 removed from the cones. 



The trees chosen for this work are described in the following 

 list (table 1), all the trees being from sixty to one hundred and 

 ten years old, and growing at an elevation of 6000 feet on a south 

 slope and on a deep granitic loam soil. The character of the 

 trees and the low crown facilitated this work, much of it being 

 done from a light ladder. 



In fertilizing the flowers the trees were crossed as is shown 

 in table 2. For convenience in reference the number is followed 

 by the character of the tree. 



After the cones were collected the following fall, they were 

 sun dried and left to open slowly. The seeds were carefully 

 cleaned by hand and weighed, and the number of seeds to the 

 pound was computed. Each lot was then sown in the nursery 

 the following spring under nursery conditions and all the lots 



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