328 JOURNAL oi' roKi'STin' 



NURSERY TESTS, I913-I916 



Northern California Seed 



days 



Average , 



Maximum ... 

 Minimum .. . . , 



Average 



SUMMARY 



Yellow and Jeffrey pines display reasonably consistent average values 

 for number of seed per pound, relation of germination to cutting test, 

 and rapidit\ of germination. Thus we might figure as follows for a 

 lot of yellow pine having a cutting test of 80 per cent: 



Number per pound 10,000 



Value by cutting test 8.000 



Probable total germination (80 per cent cutting test) . . 6,400 



Effective germination (80 per cent total) 5.120 



In other words, about 50 per cent of the total number of seed may 

 on the average be counted on to produce seedlings suitable for trans- 

 planting. 



It is hardly necessary to point out that average figures may not apply 

 in each individual case, but the chances are at least three out of four 

 that the variation will not exceed 10 per cent either way from the indi- 

 cated values. 



The other species- sugar pine, incense cedar, and the firs — .show 

 such great variability that average figures probably would apply only 

 about half the time, with a variation of 20 per cent either way. 



For such species the average number of seed per pound and cutting- 

 test values may be used in lieu of anything better, but a wide departure 

 from indicated values is to be expected in at least half the cases. 



In collecting seed, it is safe to figure on the following basis : 



P =Pr — -~ 

 K 



Pr = total production of seedlings, expressed as M. 



P = number of pounds of seed. 



N = average number of M seed per pound. 



K = constant : 2 for yellow and Jeffrey pines ; 4 for sugar pine : 5 



for incense cedar. 



