io Richard H. Bocrker 



of tap root in plants that had been grown in no shade and the 

 greatest length of lateral roots and total root system in the no- 

 shade plants. This bears out Nikolsky's experiments along the 

 same line. An interesting conclusion reached by Burns is that 

 shade reduces the temperature of the soil and delays the time of 

 germination. 



The work of Atterberg (9) which is quoted by Burns is given 

 here for completeness. Atterberg studied the relation of light 

 and temperature to the germination of pine seedlings. He found 

 that at a constant temperature of 23 C. 80 per cent, of the seed 

 germinated in the absence of light and 87 per cent, in the presence 

 of light during practically identical germination periods. Burns 

 concludes from this : " Apparently a high and changing tempera- 

 ture, light, and a moist seedbed are essential to satisfactory 

 germination." 



The investigations of Haak (5) and Pittauer (6) have very 

 little bearing upon the problem at hand. The former at the 

 mycological laboratory at Eberswalde studied the influence of 

 season, moisture, temperature, light days and dull, artificial and 

 natural light, color of light, intensity and duration of light, and 

 the influence of chemicals upon the germination of Scotch pine 

 seeds. He found that in lower temperatures germination begins 

 considerably later and proceeds much more slowly that in higher 

 temperatures, but that the final germination per cents, are about 

 the same in either case. He found that certain rays of light were 

 beneficial and certain harmful to germination. Pittauer studied 

 the effect of different degrees of light and extreme temperatures 

 upon the germination of tree seeds of certain European species, 

 viz. : beech, black locust, and various conifers. He found that 

 germination proceeds more rapidly in light than in shade and is 

 most satisfactorily accelerated in diffused light. 



Undoubtedly considerable work has been done in the United 

 States by the various forest experiment stations of the Forest 

 Service but these results have not been, as far as my knowledge 

 goes, published. In a very recent article in Science, Graves (7) 

 speaks of such work being carried on at the Wind River Forest 

 Experiment Station in Oregon. A recent discovery at this sta- 



