NURSERY PRACTICE ON THE NATIONAL FORESTS. 



31 



Covering of the seed beds during the germination period is resorted 

 to for other reasons than protection against^ rodents or birds. Chief 

 itmong these is keeping the beds as uniformly moist as possible, 

 which undoubtedly promotes the highest germination of the seed. 

 Covering also eliminates the need of such frequent waterings as are 

 necessary in uncovered beds. For the purpose of keeping the beds 

 uniformly moist, the sides and ends of the wire frame just discussed 

 are covered with building, tar, or wrapping paper, or burlap, and a 

 lath shade frame is set on top of it. Burlap is better than paper 

 because it is easier to handle, does not tear, and can be used for two 

 successive years. The lath frame is constructed as shown in figure 

 5. A complete shade or covering is obtained by laying a loose lath 

 in each interspace between those which are nailed to the frame. 

 Full or partial shade, without the side covering of burlap, is often 

 [riven the beds by means of this lath frame, some other form of a 

 low -shade frame, or high-shade frames with a slatting cover. 



TOP VIEW 





END VIEW 



Fig. 5. — Pettis seed-bed frame. 



J& 



Eecent experience has developed the fact that such shade coverings 

 ire neither necessary nor desirable in all nurseries where they have 

 )een used. This is especially true in the cooler and moister regions 

 md with seed which germinates slowly. Heat as well as moisture is 

 ;ssential for germination of seed; and in moist seed beds tightly 

 creened from the sun's rays, the temperature of the soil may be kept 

 ■o low as to delay germination considerably. This happened with 

 Douglas fir at the Wind River Nursery. Seed in seed beds without 

 ide or overhead cover, or with a cover of one thickness of burlap 

 mly, germinated twice as fast in the first month as those under the 

 egular Pettis frames. At the Cottonwood, Pilgrim Creek, and 



