CLASSES OF CI^TTINGS 



119 



i'.raftiiig not uiily causes spccil'ic variations Init that tlicsc varia- 

 tidiis may l)e |>crpetuatc(l hy ciittiiiKs. Variations in the vegetative 

 parts also seem to lie accompanie<l by variations in the root system. 



174. Browning of grape cuttings 'is due to bacteria and is con- 

 sidered a (Hsease, but P. Viala and L. Ravaz, French investigators, 

 say it is without pathological effect. Externally the cuttings re- 

 tain their normal color and when grafted readily make unions. 

 They root well and produce vigorous branches. The bacteria are 

 never found in the new growth no matter how abundant in the 

 cuttings, nor do they descend into the stock in case of grafting. 



175. Dwarf plants from cuttings.— In France cuttings taken from 

 the tips of branches of plants which have reached full development 

 but have not produced flowers, will take root under proper condi- 

 tions and produce flowers without much further growth. If the 



FIG. 106— PLAN OF CALLUSING BED 

 Notice the position of the bundles. They form calluses best when set upright. 



plants to be dwarfed produce both terminal and axillary flowers, 

 the cuttings should be taken from the least-developed flower 

 branches. The cuttings should be made about an inch under a 

 node in each case. Chrysanthemums, asters, roses, and several 

 greenhouse plants have been thus dwarfed. 



176. Callus pits (Fig. 106) are excavations in which 

 cuttings are buried for a few weeks or months prior to 

 planting. They must be made on well-drained knolls 

 fully exposed to the sun so the greatest possible use may 



