84 FIKST BOOK OF FOKESTRY 



one inch; oak, hickory, walnut, and also black locust, 

 about two inches. An old rule says that tree seeds 

 should have a cover three times as deep as the seed is 

 thick. After covering, it is well to roll or press the sur- 

 face of the ground with a board or roller. To prevent the 

 drying out of the ground it is best to give the seed bed 

 a cover of brush or else cover it with a screen. (See 

 Fig. 28.) This screen is placed on the ground until the 

 seedlings push out of the soil ; then it should be raised, 

 at first four inches, later on twelve inches for conifers, 

 and for broad-leaved trees two feet, so as not to hinder 

 the plants in their growth. This screen protects the 

 plants against sun and wind, and thus keeps them from 

 drying out. 



Some broad-leaved trees and also the pine can some- 

 times be raised without the screen, but all kinds do better 

 if thus protected ; while some kinds, like spruce and bal- 

 sam, do not get on well without it, and should have it all 

 of the first and at least part of the second year. 



Many seeds will germinate within a few weeks after 

 sowing ; some few, like ash, basswood, larch, and even 

 white pine, often " lie over," i.e., a part of the seed does 

 not come up until the second year. To prevent this the 

 seed should be soaked for several days before sowing. 



The majority of fresh or properly kept tree seeds are 

 good, and from sixty to eighty per cent of all seeds may 

 be expected to germinate ; but of those of balsams, birch, 



