200 



Principles of Plant Culture. 



weeks, and then be thoroughly washed before being em- 

 ployed 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 with cuttings 

 placed in it. 



369. Methods of Controlling Humidity. Where moist- 

 ure needs to be controlled with especial care, as in prop- 

 agating delicate plants from green cuttings, or in herba- 

 ceous grafting (393), the planted cut- 

 tings or the grafted plants are often 

 covered with bell -jars. To guard 

 against sudden fluctuations in temper- 

 ature, a larger bell -jar is 

 sometimes placed over a 

 smaller one. By means 

 of a bell -jar with a tight- 

 fitting ground plate, 

 evaporation may be 

 wholly prevented from 

 cuttings or plants, if de- 

 sired. Propagating beds 



FIG. 96. Propagating bed covered with are often Covered With 



glazed sash. glazed sash, iii addition 



to the glass roof of the house, to assist in maintaining a 

 moist atmosphere about the cuttings (Fig. 96). 



For convenience, we separate propagation by cuttings 

 into two divisions, viz., propagation by cuttings from 

 dormant and from active plants. The requirements of 

 these two classes differ in some respects. 



a Propagation ~by cuttings from dormant plants. 



370. The Time to Make the Cuttings. We have seen 

 that plant processes may not be wholly suspended during 



