ORIGIN AND IMPROVEMENT OF FRUIT 337 



and towns of Massachusetts. The named varieties which 

 are now grown commercially are Goethe, Massasoit, Wilder, 

 Lindley, Gaertner, Agawam, Merrimac, Requa, Aminia, 

 Essex, Bariy, and Herbert. These grapes are of exception- 

 ally high quality, combining the richness of the European 

 with the general type of the American grape; but unfortu- 

 nately these hybrids are usually somewhat deficient in vigor, 

 hardiness of root or vine, self-fertility or pi'oductiveness. 



299. Breeding disease-resistant fruits. — Most of the 

 definitely plamied experiments in breeding of deciduous 

 fruit-trees in the United States and Canada have had as 

 their purpose the securing of hardier varieties. Of equal 

 importance to the orchardists of the large fruit regions of 

 this country is the problem of securing fruits resistant to 

 such diseases as blight {Bacillus amylovorus), peach yellows, 

 and the like, and breeding seems to be the ray of hope to 

 these breeders. The selection of disease-resistant individuals 

 would be the first means of attacking this problem, since 

 man}^ other kinds of plants have produced disease-resistant 

 strains, as for example, flax, cotton, and melons. In these 

 genera, however, there is a new sexual generation each year, 

 which affords an opportunity for variation that does not 

 obtain within a clone. It, therefore, remains for the breeder 

 to combine a variety or species which is immune to the 

 trouble in question with a variety of commercial importance 

 subject to it. Thus, if a Bartlett subject to blight is crossed 

 or hybridized with a blight-free pear, there is a possibility 

 of obtaining a fruit as valuable as the Bartlett but with the 

 "factor" for blighting absent. This possibility rests on the 

 assumption that disease-resistance or susceptibihty is a unit 

 character and thus jiermits of recombination. 



300. Stocks for pears. — According to the findings of 

 Reimer, the following species of pear are quite blight- 

 resistant: Pyrus sinensis, P. ovoidea, and P. Pashia {vario- 



