72 Richard H. Boerker 
for Pinus ponderosa. In the case of this species the difference 
was often as much as 100 per cent. ; usually the difference in other 
species did not exceed 50 per cent. Schotte (23), of the Swedish 
Forest Experiment Station, has shown that the size of the seed 
and the size of the cones decrease with increasing age of the tree 
in the case of Scotch pine. The work (24) done on seeds by 
certain forest experiment stations in Europe in 1907 with spruce 
showed that seeds from large cones germinate earlier than those 
from small cones; that the largest cones produce the largest and 
heaviest seeds and hence the largest plants; and that the effect of 
the size of seed upon the life of the plant has been noticed only 
in the first two years of its growth. 
In Busse’s (25) experiments pine seeds were graded by means 
of a Kayser centrifuge into three grades according to weight. 
The heaviest seed made up 68 per cent. of the stock seed, the 
medium weight seed 27 per cent. and the light seed 5 per cent. 
He recommended the first grade for field sowing but said that the 
third grade should not be used. Sprout tests did not show any 
differences in germination results. Centgraf (26) examined 247 
tests of pine seed as to the relation of the weight of 1,000 grains 
to their germination. He failed to find a relation between weight 
and germinative energy or germination per cent. In fact he 
found that the heavier seed averaged a smaller germination per 
cent. than the light ones. He concluded that the slower germina- 
tion of big seed is probably due to a thicker seed coat of the 
heavier seed which determines in part its weight and which takes 
up water more slowly than thin coats of light seed. Some of 
these results do not agree with the many experiments made by 
foresters in Europe. These tests being made for commercial 
purposes cannot therefore be taken as conclusive. 
While the size and weight of seed has been recognized as a 
factor in germination it also has been recognized as a factor in 
the early development of the seedling as has been indicated in a 
few instances above. One finds statements in regard to this rela- 
tion quite common in silvicultural works but very little material 
to substantiate these opinions. The view held by many writers is 
summarized very well by Schlich in his Manual of Forestry 
(27): 
