FOREST TREE SEED AND SEED COLLECTING 135 



vestigations have but little practical application. Observations 

 on the mast of beech show that in a specific district in Germany 

 there were 1 full seed year, 3 half seed years, 4 partial seed years, 

 and 17 off years or failures between 1787 and 1811. The total 

 amount of mast produced in these 25 years equaled that of 3 full 

 seed years; or, in other words, the equivalent of a full seed year 

 occurred at 8-year intervals. Between 1850 and 1873 in the same 

 district the beech produced the equivalent of a full seed crop at 

 intervals of 12 years. Other observations on the beech made 

 during the same period in other localities showed the equivalent 

 of full seed years at 7-year intervals, suggesting the effect of 

 locality upon seed production. A more comprehensive study of 

 seed production under a definite plan was carried on for 20 years 

 by the Prussian government, based on an ocular estimate of the 

 amount of seed produced by the dominant trees in the stand. 

 Schwappach x in the summation of the data in 1895, although 

 appreciating its heterogeneous character and its non-applicability 

 to specific localities, was able to determine the average seed pro- 

 duction of the various Prussian species from the following formula : 



. a X 100 + b X 50 + c X 25 



Average production = - . 



a + 6 + c-\- d 



a = number of full seed years. 

 6 = number of medium seed years. 

 c = number of poor seed years. 

 d = number of failures. 



The amount of seed produced in a full seed year is designated 

 by 100, in a medium seed year by 50, in a poor seed year by 25, and 

 a failure by 0. 



Applying this formula to the various species for the time over 

 which the observations were made the average annual seed pro- 

 duction in per cent of a full crop was as follows: 



Birch 44.8 Silver fir 34.5 



Hornbeam 42.0 Ash 33.3 



Alder 39.9 Oak 17.1 



Scotch pine 37 . 6 Beech 16 . 2 



Norway spruce 37 . 1 



1 Schwappach, A.: Die Samenproduktion der wichtigsten Waldholzarten 

 in Preuszen. (Zeitschrift f. Forst- u. Jagdwesen, S. 147-174. 1895.) 



