Germination of Forest Trees 1 1 



tion showed that the seed of Pinus monticola of Idaho lies in the 

 duff and litter beneath the mature stands for years and then 

 germinates when the ground is exposed to direct lighting. This 

 is mentioned here, merely as another instance of the many of 

 record in which it is assumed that light is to a large degree re- 

 sponsible for the germination of certain tree seeds. 



Practically the only work of any importance on record concern- 

 ing the effect of soil moisture and soil texture upon the early 

 development of forest trees is that of Tolsky (8). He studied 

 the relative effect of sandy and black soils upon the structure of 

 the root system of Scotch pine. He found on black soils that 

 pine developed principally vertical roots while on sandy soils 

 superficial roots predominate. In rich soils roots are guided in 

 their development by moisture, while in poor soils like sand, 

 activity is directed mainly towards extracting nutrition from the 

 soil. In poor soils nutrition is spread over a large area and in 

 order to get it in sufficient quantities trees need numerous roots. 

 Whatever the cause might be, Tolsky found more lateral roots 

 and more superficial roots in the case of trees grown in sand, and 

 this may be taken as the most significant part of his work. 



Before discussing the present investigations, I feel that it would 

 be profitable to briefly summarize the edaphic factors of the 

 habitat with special reference to the physical properties of the 

 soil which play a physiological role in the germination of the 

 seed. 



Classification and Resume of Habitat Factors 



The complex of climatic, edaphic, and biotic factors which 

 influences the life, growth, and reproduction of a plant is known 

 as its habitat. The study and investigation of habitats as entities 

 avails us very little unless we analyze a habitat into its component 

 parts and investigate each of these parts by itself. 



Clements (i) classifies habitat factors into physical and biotic. 

 The former have to do in general with inanimate objects and the 

 latter with human beings and animals. He further divides phys- 

 ical factors into climatic and edaphic. Climatic factors are atmos- 

 pheric in their nature and the edaphic factors are concerned with 



