CUTTINGS 65 



Unless cuttings are so treated the air will get into the sand, and the 

 base of the cutting will dry. After setting the cuttings, water them 

 thoroughly and cover them with newspapers or a cheesecloth screen. 



THE ROOTING TEMPERATURE 



To induce root action rather than top growth, it is agreed that 

 there should be some sort of bottom heat; that is, the temperature 

 of the sand should be greater than that of the air. In greenhouses 

 this is attained by running several pipes under the cutting benches. 

 For Summer rooting out of doors, hotbeds may be used and fresh 

 and fermenting manure employed as the source of heat. The florist 

 and nurseryman prefer to have a difference of from 5 degrees to 10 

 degrees between sand and air. 



DAMPING-OFF FUNGUS 



The "damping-off" fungus is often encountered in the cutting 

 bench. The cuttings decay at the surface of the sand, the tops 

 often remaining green some time after the stem has blackened. 

 Excess of water in the sand or air favors the spread of the disease. 

 A higher temperature than the plant requires and close conditions 

 are other factors. Formalin, used at the rate of one part formalin 

 to fifty of water, using two quarts to a foot of sand, will kill the 

 fungus, but the cost is rather prohibitive. Allowing the sun to 

 enter the house and letting the bench become rather dry, will help 

 control it when the plants are in the bench. It is suggested that 

 peroxide of hydrogen be used to supply oxygen to the sand and air. 

 Definite proportions have not been accurately determined. 



THE CALLUS 



When a cutting starts to root it gradually produces a layer of 

 spongy tissue over the cut surface. This is a callus and usually 

 precedes rooting. Conditions which favor callus formation also favor 

 root formation. Good callus formation, therefore, indicates that 

 conditions are proper. Leaf calluses form on the veins (note fig. 25) . 

 The callus is first a wound protection, but later the cells are absorp- 

 tive and even go so far as to produce organs lost as a result of the 

 wounding. 



MONOCOTYLEDONOUS PLANTS 



The monocotyledonous plants, such as the grasses, Lilies, As- 

 paragus and Aroids, root in a different way than the dicotyledonous 

 plants. A callus is rarely formed, but the cut surface becomes corky 



