Propagation by Cuttings. 193 
streams or lakes may generally be safely used without wash- 
ing, but that dug from sandpits should in most cases be ex- 
posed to the air for a few weeks, and then be thoroughly 
washed before being employed for cuttings. The same sand 
should be used for but one lot of cuttings as a rule, for it is 
liable to become infested with fungi that may work havoc 
in the cuttings placed in the propagating bed (368). 
369, Methods of Controlling Humidity. Where 
moisture needs to be controlled with especial care, as in 
propagating delicate plants from green cuttings, or in her- 
baceous grafting (393), the planted cuttings or the grafted 
plants are often covered with bell-jars. To guard against 
sudden fluctuations in temperature, a larger bell-jar is some- 
times placed over a smaller one. 
By means of a bell- 
jar, with a tight-fitting 
ground plate, evapora- 
tion may be wholly 
prevented from cut- 
tings or plants, if desir- 
\ ed. Propagating beds 
== are often covered with 
glazed sash, in addition 
to the glass roof of the 
house, to assist in main- 
taining a moist atmos- 
Fig. 95. Propagating bed covered with glazed phere about the cut- 
sash. tings (Fig. 95.) 
For convenience, we separate propagation by cuttings 
into two divisions, viz., propagation by cuttings from dor- 
mant plants, and from active plants. The requirements of 
these two classes differ in some respects. 
