2 BULLETIN 195, U. S. DEPARTMENT OF AGRICULTURE. 
material variation between the total potato production of the two 
countries. 
The modern tendency toward the development of potato-growing 
centers in widely separated sections of the United States, as, for ex- 
ample, Aroostook County, Me., the Norfolk and Eastern Shore 
trucking regions of Virginia and Maryland, the Red River Valley of 
Minnesota and North Dakota, the Kaw Valley of Kansas, the Greeley 
and Carbondale districts of Colorado, and the San Joaquin and Sac- 
ramento Valleys of California, has created a demand for varieties 
of potatoes especially adapted to cultivation in those sections. 
This condition, coupled with the presence of numerous diseases of 
the vines and tubers, from which frequent and oftentimes severe 
losses have resulted, has caused many inquiries to be made regarding 
the possibility of developing new varieties or strains possessing 
certain specific qualities not embodied, at least to the same degree, in 
those varieties now under cultivation. 
This demand upon the plant breeder has served to emphasize the 
necessity, as well as the desirability, of attempting to develop, 
either through breeding or selection, new varieties or strains of pota- 
toes which shall possess a greater degree of resistance to the parasitic 
fungi which now prey upon the plants and tubers. Another fruitful 
field of investigation well worth the attention of the plant breeder is 
the development of potato varieties that are better adapted to certciin 
sections of our country. These adaptational characteristics may be 
either earliness or lateness, drought resistance or heat resistance, or an 
ability to succeed in heavy or in light soil; they may be productive- 
ness, shape of tuber, quality of tuber, starch content, or, in fact, any 
distinct quality which would make a variety especially desirable for 
cultivation in a given locality. 
POTATO BREEDING AND SELECTION DEFINED. 
In order that there may be no confusion in the mind of the reader 
as to what is meant in this bulletin by the term " breeding/' the writer 
has thought it best to make a clear-cut distinction between "breeding" 
and "selection." 
Breeding is here employed in the sense of sexual reproduction. 
Selection implies, in the case of the potato, the isolation and 
asexual propagation of desirable strains or types. 
Breeding can only be successful when it goes hand in hand with 
selection. Selection, on the other hand, is not dependent upon breed- 
ing for results. 
LLMITATIONS OF BREEDING AND SELECTION. 
Broadly speaking, the limitations of breeding are not simply those 
found within the confines of our cultivated varieties of potatoes, but 
those embraced by the whole range of the tuber-bearing solanums. 
