physiologically considered. 159 



as much moisture through the face of the cut as it loses in ordi- 

 nary circumstances by evaporation, yet no sooner is it placed in 

 very dry air or in a draught, or exposed to the sun's rays, than a 

 disproportion takes place between them. When this is the case, 

 more watery particles are lost through evaporation than are 

 raised in the body of the wood, which is very easily perceived 

 in fleshy-leaved plants. On this account, hotbeds and houses 

 prepared on purpose for propagating should be used, in which 

 the outer air can be excluded, a moist temperature maintained, 

 and in very warm sunshine a dense shade can be given. Bell- 

 glasses should be placed over the more difficult-rooting cuttings, 

 to protect them from all external influences which might destroy 

 them before they made roots. The most proper form of bell- 

 glass is that which gradually tapers from the base to the top ; 

 as from glasses of this shape the moisture, which adheres to the 

 inside in the form of drops, runs gradually off without the drop- 

 ping so injurious to cuttings. This disadvantage is found in 

 all other forms more or less, such as those that are round at the 

 top, or cylindrical with the top bluntly truncated, and also in 

 beer glasses which are often applied to this purpose. The most 

 unsuitable glasses, which are, however, much used, are those 

 small at the base, and swelling out like a globe. 



The enclosed air under the glasses will soon lose its oxygen, 

 through the respiring process of the plants within, and also be 

 vitiated by other exhalations ; and, if it is not changed, it gene- 

 rates mould, and the cuttings lose their fresh appearance. For 

 this reason, the glasses, if possible, should be daily ventilated 

 and wiped ; or what is still better, as it will entirely renew the 

 air, dipped in a vessel of cold water, and well shaken, so that 

 too many drops of water may not remain on the glass, although 

 they are not so injurious to the cuttings. In an extensive esta- 

 blishment, this operation requires too much time, and therefore 

 round holes, of about from ^ in. to f in. in diameter, should be 

 made at the top of the glasses ; and these will prove very ser- 

 viceable, if the pans stand on a warm platform in the houses 

 or beds prepared for the purpose. In small gardens, where the 

 cuttings are placed with other plants in the houses on the bed or 

 shelf under the windows, glasses without holes would be pre- 

 ferable. When the ground is warmed to about 10° R. (54'5° Fah.) 

 it is better, with some few exceptions, such as the Zaurus species, 

 to place the glasses inside of the pans, so that the temperature 

 within may not rise too high. When the warmth is not so 

 great, they may also, without injury, be placed on the outside of 

 the edge of the pot. 



The cuttings themselves should not be stuck too close toge- 

 ther, and all the leaves should be left on, which are essential for 

 elaborating the absorbed and deposited nourishment ; removing 



