54 



Richard H. Boerker 



loam, four in sand, and four in gravel. It is significant to note 

 the large number of species in this table that germinate well in 

 the gravel. 



On pages 52 and 53 are given the germination curves of Pinus 

 ponderosa (S. D.), Pinus contorta, Pseudotsuga taxifolia (N. 

 M.) and Pinus ponderosa (N. M.). These curves show that the 

 germination usually begins earlier in the sand or gravel, that the 

 curve rises more rapidly for these soils and that the germination 

 per cent, is usually higher. f 



Table IX gives the results for the Pacific coast species. ^Out 

 of 9 species, two germinated first in the loam, the others ger- 

 minated first in either the sand or gravel. Three had longest 

 germination periods in the loam and six in either the sand or the 

 gravel. Only one species, Libocedrus decurrens, showed the 

 highest germination per cent, in the gravel, while six species 

 germinated highest in the sand. 



On page 55 are given the germination curves of Pinus pon- 

 .derosa and Pinus jeffreyi both from California. These curves 

 show substantially the same facts as those for the Rocky Moun- 

 tain species. These curves show that Pinus ponderosa does not 

 germinate so well on gravel as does Pinus jeffreyi a fact which is 

 significant when it is remembered that the latter will grow on 

 much poorer soil than the former. 



TABLE IX 



The Effect of Soil Texture on Germination 



Pacific Coast Species 



Species 



Loam 



03" 



o >, 

 'u PJ 



Sand 



,".« 



su 



Gravel 





Pinus ponderosa (Calif.) 



Pinus jeffreyi 



Pinus lambertiana 



Abies magnified 



Libocedrus decurrens. . . . 

 Sequoia washingtoniana . 



Tsuga heterophylla 



Picea sitkensis 



Larix occidentalis 



Pseudotsuga taxifolia. . . 



28 



61.0 

 22.0 



2-S 

 18.0 

 6.0 

 7.0 

 0-5 



22.5 



68.0 



33-0 

 9.0 



3° 

 13-5 

 16.5 



3-0 

 31-0 



6.0 



64 



17.0 



19.0 

 9.0 

 5-o 



22.0 

 0.5 

 1-5 



24-5 



38 I 44 5.0 36 48 6.0 



