88 OUR NATIONAL FORESTS 



time required for the germination of seed extracted 

 with or without artificial heat; and the most 

 economical type of seed-extracting plant. Studies 

 have been made upon the comparative germina- 

 tion of tree seeds in the field and the greenhouse. 

 The ultimate success of the plantations being estab- 

 lished on the National Forests in a large degree de- 

 pends upon the character of the seed used. Hence 

 studies are being conducted of the effect of altitude, 

 soil, age of the tree, density of stand, insect damage 

 and disease infection, and other factors that affect 

 the mother tree, upon the character of the seed col- 

 lected from those trees, and the growth and form 

 of the resulting seedling. Also tests to show the 

 effect of the source of seed on the form and growth 

 of young seedlings have indicated very clearly that 

 with all species the seed grown in the locality where 

 the trees are to be planted give as a rule better re- 

 sults than seed imported from another region. 



Nursery Studies. Nursery studies endeavor to 

 show the most efficient methods for growing young 

 trees for field planting for each species of trees. 

 It is of great importance to know how much seed to 

 sow per foot in the nursery beds ; what is the best 

 time (spring or fall) for sowing; to what depth the 



