Germination of Forest Trees , 71 



terial will produce smaller seeds than in cases where there is a 

 great accumulation. It has been repeatedly shown that after a 

 seed year the amount of accumulated food in the medullary rays 

 and other food accumulation centers is reduced to a minimum. 

 The site upon which the tree grew, naturally, is intimately con- 

 nected with the amount of food material available for the embryo 

 of the seed. For the same reason the climatic variety of the 

 tree probably affects the size of the seed. At least, it is common 

 knowledge that the California variety of Pinus ponderosa has 

 seeds which may weigh from three to four times as much as 

 those of the South Dakota variety. While most of these points 

 remain to be proven experimentally, they have been indicated to 

 the writer by various experiences and are put forth as interesting 

 hypotheses awaiting experimental proof. Whatever the cause of 

 the varying size of seeds is, it is quite evident from the amount 

 of literature on the subject that this phenomenon has attracted 

 considerable attention in recent years both in silviculture and 

 agriculture. 



That heavier and larger seeds furnish a better germination per 

 cent, than light ones has been recognized for a long time by 

 European silviculturists. The physiology of germination indi- 

 cates that large seeds should succeed better, and repeated ex- 

 periments by Biihler, Friedrich, Haack, Eisenmenger, and others 

 establish this beyond much doubt. In fact forestry practice 

 throughout Europe and especially in Prussia shows that smaller 

 seeds produce fewer plants per hectare than larger ones in broad- 

 cast sowing. Favorable and unfavorable site and season condi- 

 tions produce far less variation in the final results in cases where 

 heavy seeds are sowed. 



In 1904 Blumer (22) conducted at the seed laboratory of the 

 United States Department of Agriculture a series of tests upon 

 certain American species of tree seeds. Pinus ponderosa from 

 the Rocky Mountains and Pinus divaricata showed the highest 

 germination but Pinus ponderosa from Oregon germinated ex- 

 ceedingly slowly, a feature which also characterized Pseudotsuga 

 taxifolia from the Pacific Coast. He noted great variation in 

 the number of seeds per pound for the same species, especially 



