BOTTOM HEAT 



FIG. 77 PIPE-WARMED HOTBED 



a, plant support; b, hot- water pipes; c, \ 

 tanks. 



greenhouse benches. (Fig. 76.) When necessary to in- 

 tensify the heat the space beneath the bench is walled 

 in tightly to confine the heat. In a small way bell 

 glasses and similar utensils (Fig. 32) are placed over 

 seeds, seedlings or cuttings on the benches or merely over 



a soup plate or a sau- 

 cer filled with sand 

 which covers the cut- 

 tings. Sun heat alone 

 is often used in such 

 cases. 



5. Propagating ovens 

 (Figs. 36, 37) are some- 

 times used for small 

 lots of seeds or cut- 

 tings, as in schools 

 where teaching the 

 principles of plant cul- 

 ture rather than com- 

 mercial work is the aim, where the room temperature 

 falls low during the night and where there are no green- 

 house facilities. 



They are generally heated by lamps and are usually more or less 

 insulated boxes with only three to five cubic feet content. In the 

 bottom is a chamber for a kerosene lamp reached by a door for fill- 

 ing and other attention. Above the lamp is a 

 galvanized iron water tray and above this a 

 perforated floor. Next above is the sand tray 

 in which the cuttings are placed for propaga- 

 tion. The cover is of glass. By means of the 

 lamp the water is made to give off vapor which 

 keeps sand and air above it warm and moist. 

 Regulation of the size of the flame and of the 

 ventilators will control both temperature and 

 humidity in the propagating chamber. 



135. Bottom and air heat effects. 

 All growth in plants results from 

 a stimulus of some kind. Various agents may 

 bring it about ; for instance, ether vapor. So far, 

 however, as the commercial plant propagator is con- 



SINGLE LIGHT 

 MELON FRAME 



