liOTTOM HEAT 



91 



FIG. 81 



GLASS COVERED CUT- 

 TING FRAME. 



must be avoided, because the reverse are necessar}- to rout 

 making, which should always, except perhaps with tuber 

 and root cuttings, precede growth of stem and leaf. 



The philosophy of this is apparent; for when growth 

 starts, the foods stored in the plant are moved rapidly to 

 the part that has become active. 

 Hence if the part be above ground 

 all the food goes there ; in fact, is 

 removed from the part that should 

 form roots. Result, breakdown and 

 death. Con\'ersely, if the air be 

 cool and the soil sufliciently warm 

 from start to finish the cuttings soon 



develop calluses and roots (Fig. 91) upon which to]i 

 growth normally depends. Hence such conditions should 

 be maintained, because if cuttings are properly planted 

 growth will occur only below ground, where it should 

 be. \\'hen once the roots have begun to grow below 



ground plant food ma- 

 terials can be taken u\) 

 b_\- the roots and trans- 

 ferred to the parts above 

 ground. As soon as 

 green matter has been 

 developed b}- the ex- 

 panding buds (already 

 present in green wood 

 and leaf cuttings) it can 

 work over the crude 

 food in the presence of 

 sunlight and the full 

 functions of plant 

 growth will have started 

 properlv above and be- 

 low ground. 



Mature wood cuttings 

 FIG. 82— SWEET POTATOES AND VINE ^an Stand greater hard- 



