50 



box is placed a common cylinder stove, with smoke-pipe to 

 the chimney. Inside the stove is an iron pipe, bent in a 

 spiral. This coil, which is directly in the fire, is connected by 



5i, Barnard'' s propagating-tank. 



pipes with the tank, one pipe 

 leading to one side of the 

 partition and the other to the 

 opposite side, as shown in the 

 drawing. If water is placed 

 in the tank, it will fill the 

 pipes and form a continuous 

 circulating system through 

 the pipes and up one side of 

 the box past the end of the 

 partition, and down the other 

 side. A fire in the stove causes the water to circulate 

 through the tank and impart to the bed a genial warmth. 

 There are various tanks designed to rest upon the pipes 

 in a greenhouse. The principle of their construction is 

 essentially the same as of those described in previous pages, 

 — bottom heat, a tray of water, and a bed of soil. Earthen- 

 ware tanks are commonly employed, but a recent English 

 device, Fig. 55, is made of zinc. It is about 7 inches deep, 

 and holds an inch or two of water in the bottom. A tray 5 

 inches deep sets into the tank. The water is supplied 

 through a funnel at the base. 



Cuttings usually "strike" better when they touch the 

 side of the pot than when they are wholly surrounded by 

 soil. This is probably because the earthenware insures 

 greater uniformity in drainage than the earth, and supplies 

 air and a mild bottom heat ; and it is possible that the 

 deflection of the plant food towards the side of the pot, 

 because of evaporation therefrom, induces better growth 



