PROPAGATION BY CUTTINGS. <O 



3RD. MEANS OF PROMOTING THE ROOT-GROWTH ON 

 CUTTINGS. 



The evolution of roots can only take place in sufficiently 

 warm and moist surroundings, without, however, being ex- 

 cessively so. In practice, the greatest difficulty met with, is 



Fig. 36. A. Vine resulting from a short cutting. B. Vine resulting from a long cutting. 



to prevent the cutting from drying before it is able 

 to provide for the water it evaporates. Certain American 

 species are very refractory on account of the time elapsing 

 between the bursting of the buds and the development of 

 the roots ; this forces the plant to evaporate largely before 

 it is able to draw the necessary 

 water from the soil. For 

 instance, while the V. Riparia, 



V. Labrusca, and V. Rupestris 

 strike easily from cuttings, V. 

 JZstivalis, and more especially 



V. Berlandieri, strike with difficulty; while I". Candicans 

 and V. Rotundifolia are almost impossible to multiply from 

 cuttings. 



The means of remedying this difficulty have been studied 

 with great care, especially with regard to the ; V. Berlandieri, 

 which contains, as we have seen, most valuable forms for 



