Propagation by Cuttings. 189 
leaves, refuse hops or tan-bark. The material intended for 
heating, if fresh, should be thrown into a pile of sufficient 
size to generate heat, several days before it is desired for 
use; and unless already moist, it should be moderately 
sprinkled with water. In order that all the material may 
reach the same 
stage of fermen- 
tation, the mass 
should be made 
into a new pile « SW 
after the heating 
sturts vigorous- 
ly, as is indica- 
ted by vapor ris- 
ing from the Fie. 93. Cross section of hotbed in pit. The frame is 
heap, and the banked upalittle with earth. (After Greiner). 
outer part of the mass should be placed in the center of the 
new pile. Leaves ferment slower than the other materials 
above named, and hence may often be advantageously mixed 
with them to lengthen the period of fermentation. 
Heat is economized by placing the fermenting material 
in a pit in the ground, but hotbeds are often made above 
ground. The hotbed pit should be in a well-drained and 
sheltered place, and two to two and one-half feet deep. In 
this, the heating material should be moderately packed, 
until the pit is nearly or quite full. The frame may then 
be placed over the pit, after which the heating material 
should be covered with soil and the sash put on to confine 
the warmth. Within a few days after covering with the 
sash, the fermenting material usually generates a rather 
violent heat, which should be permitted to decline to about 
90° F., before planting seeds or cuttings in the hotbed. The 
