210 



PRINCIPLES OF PLANT CULTURE 



FIG. 104. Rooted cutting of 

 coleus. 



Since the presence of leaf surface upon the cutting 

 greatly promotes transpiration (74), propagation from 



green cuttings is scarcely prac- 

 ticable in the open air. Bottom 

 heat (362), with a compara- 

 tively low air temperature, is 

 especially important with green 

 cuttings, in order that the food 

 prepared in the leaves may be 

 devoted to the formation of 

 roots. A small leaf surface on 

 the cutting is generally prefer- 

 able to a larger one; in many plants, a portion of a 

 single leaf is sufficient. The leaf surface should in no 

 case be permitted to wilt; hence the cuttings should 

 generally be sprinkled with water as soon 

 as made. Figs. 104 and 105 show forms 

 of greenwood cuttings. 



378. Care in making green cuttings. 

 Especial care is necessary in propagating 

 plants from green cuttings. In planting the 

 cuttings, the material of the propagating bed 

 should be put in close contact with the stems, 

 and no leaves of the cuttings should be 

 covered. Since roots cannot form without 

 oxygen, the bed must not be so freely watered 

 as to exclude all air. Transpiration should 

 be reduced by sheltering the cuttings from 

 the direct rays of the sun. Movable screens, 

 used during sunshine only, are preferable to whitening 

 the glass, which causes too much shade when the sun 

 is not shining. 



Damping-off, a much-dreaded disease causing cuttings 



105. 

 Cutting of 

 chrysanthe- 

 mum. 



