tflTRSERY PRACTICE ON THE NATIONAL FORESTS. 39 
are required to put the slatting on or take it off, and it takes from 7 
to 10 days per acre (two men from 3J to 5 da}^s) to complete the 
operation. The slatting is inconvenient to remove so that small areas 
under it can not be shaded or uncovered according to the require- 
ments of the different species. The posts do not readily permit of 
plowing and harrowing in preparing the ground, so that these oper- 
ations are more expensive ; and they also interfere in the laying out, 
sowing, and covering of the beds. Rain collecting on and dripping 
from low points on these frames washes out either seed or seedlings. 
The frames do not hold a mulch in place well. At Forest Service 
nurseries high frames are being used less and less. 
In case of emergencies, brush frames can be used. The principle 
of these is to use brush to furnish the shade. In high frames addi- 
tional light stringers may be necessary to support the brush because 
of its irregular size. For this purpose wire serves very well. Brush 
frames have some advantages ; there is no material quite equal to 
brush as a light filter; it is cheapest when the nursery is located in 
a remote region with poor communication by wagon road to a source 
of lumber supply; it is more easily removed after a heavy snow than 
sections of lath roofing; and it can quickly be put up if a special 
need for shade should suddenly develop at a nursery. On the other 
hand, it has disadvantages; the leaves and small twigs are continu- 
ally falling on the plants and must be removed to prevent smother- 
ing; the brush is very inflammable, and it is not easy to spread, es- 
pecially on high frames. Brush when used should be of as heavy 
foliaged species as are available. 
KEMOVAL OF SHADE FEAMES. 
The most critical time in growing plants is the 6 weeks follow- 
ing germination, for during this period they are most subject to 
damping-off. Shading and watering have an important bearing upon 
the control of this disease. If germination occurs during cool 
weather or during hot weather when the surface soil is extremely 
wet, the shade frames should be removed. As soon as the soil sur- 
face becomes dry in hot weather, full sunlight is dangerous. It may 
give rise to " white-spot " injury, regularly confused with damping- 
off, but caused by overheating the surface soil. The object of the 
removal of shade frames is to dry the surface soil and lower the air 
humidity over the beds. This condition is least favorable to the 
development and spread of the damping-off fungi. 
When practicable, the shades should be removed during periods 
of rainy weather. The water reaches the soil better and the plants 
become somewhat accustomed to a greater degree of light. It is 
generally held that during late summer and early fall the shades 
