PROPAGATION 71 



slit back to enter the bud against the wood. Frequently 

 buds develop several years later from the stock and unless 

 they are destroyed may rob the budded portion of food and 

 kill it. In all cases of grafting and budding wound hormones 

 are probably formed to stimulate rapid cell division. Only 

 varieties that will readily form a strong union of the new 

 tissue should be used for scion and stock. We do not know 

 why all woody plants cannot be grafted on each other, as for 

 example cherry on apple, but we know the tissues will not 

 unite. 



Layering is a method of propagation similar to cuttings 

 except that a shoot or branch is held against the ground or 

 even covered at places with soil until roots grow, before sever- 

 ing it from the parent plant. Cutting through the bark often 

 hastens rooting. Roots will usually grow opposite each bud 

 as it develops a shoot, after which the cuttings may be made. 

 This method is more successful with plants that root poorly. 



Runners may be formed naturally, as in strawberries, and 

 the new plants transplanted when they are well rooted. This 

 is a form of layering. 



There are several forms of propagation among the plants 

 that have bulbs, corms, rhizomes, tubers, etc., but for these, 

 special reports should be consulted. 



REFERENCES 



Adriance, G. W., and F. R. Brison, Propagation of Horticultural Plants, McGraw-Hill 

 Book Co., 1939. 



Bailey, L. H., Manual of Gardening, The Macmillan Co., 1925. 



Hitchcock, A. E., and P. W. Zimmerman, "Effect of Growth Substances on the Rooting 

 Response of Cuttings," Contributions from the Boyce Thompson Institute, vol. 8, 

 pp. 63-80, 1936. 



Zimmerman, P. W., and A. E. Hitchcock, "Response of Roots to 'Root-Forming' Sub- 

 stances," Contributions from the Boyce Thompson Institute, vol. 7, pp. 439^145, 

 1935. 



