ORIGIN AND IMPROVEMENT OF FRUIT 333 



Nurseiymen and fruit-growers will continue to search for 

 superior strains of the old varieties and it cannot now be 

 stated with absolute assurance that some success will not 

 crown their efforts. 



294. Graft-hybrids^ represent one of the most interesting 

 phenomena that occurs in nature. They remained unex- 

 plained for centuries although many of them had been ob- 

 served. A graft-hybrid may be defined as the combination 

 of the stock and cion tissues into a form which is intermediate 

 between the two. The explanation for these queer ''freaks" 

 or chimeras was not clear until they had been produced 

 artificially. It appears that either there is a mingling of 

 the tissues at the point of contact of the graft or else that an 

 adventitious bud arises where the callous has formed, which 

 partakes of both tissues. The result is either a pcriclinal 

 chimera in which one tissue envelops the other (the hand-in- 

 glovc type) or a sectorial chimera in which the two tissues 

 occur side by side on the same stem, leaf, or flower, yet each 

 retains its independent form. In at least one case, the 

 number of chromosomes in the graft-hybrid is the same as 

 if the hybrid were sexual in nature, thus being a true hybrid. 



An apple called Sweet and Sour, which is described in 

 "The Apples of New York" and is occasionally seen, is 

 probably a graft-hybrid. The apple is somewhat ribbed 

 and this ribbed portion is green while the part between is 

 yellowish. The flesh beneath the green skin is distinctly 

 acid, while that under the j^ellowish skin is mildly sub-acid 

 or sweetish. 



295. Breeding the grape. — The early varieties of Amer- 

 ican grapes wcr(> s(>cdlings of merit derived principally from 

 Vitis Labrusca. The early efforts to grow the European 



* Popenoe, Paul. Plant chimeras. Jour. Heredity, Vol. 5, p. 521. 

 Dec, 1914. Ca.stle, W. E. An apple chimera. Jour. Heredity, Vol. 

 5, pp. 200-202. 1914. 



