POTATO BREEDING AND SELECTION. 27 
(3) That the depth of the eyes, a character almost always maintained in asexual 
reproduction, also offers, without apparent cause, examples of bud variation. 
SELECTION METHODS. 
TUBER-UNIT METHOD OF SELECTION. 
A method advocated by Webber, 1 known as the tuber-unit method 
of selection, has recently received considerable attention. This 
nun hod consists in planting select tubers of a variety in such a way 
that the plants from each tuber will be definitely isolated from each 
of the other tuber units. The tuber is cut longitudinally through its 
axis into four as nearly equal parts as possible, aiming in all cases to 
cut through the cluster of eyes surrounding the terminal one. The 
quarters are planted consecutively, and a double space is left between 
the four units of each tuber in order that they may be more easily 
distinguished from one another. When the plants have reached their 
full development, each unit should be carefully dug and again exam- 
ined. If it is found that some of the marked units produce a uniform 
lot of tubers, both as to shape and size, and are equal to or more pro- 
ductive than the general average of the variety, they should be saved 
for further trial. By this method it is claimed that not only can 
uniformity in size and shape be secured but the productiveness of 
the variety may be increased, because of the fact that selection tends 
to weed out all of the unproductive plants. By continuing this line 
of work one may finally secure an excellent commercial strain of 
potatoes. 
HILL SELECTION. 
Another method, varying slightly from the one first described, con- 
sists in making individual hill selections in the potato field at digging 
time. The particular qualities sought after are practically the same, 
viz, greater uniformity in size and shape and a maximum number of 
merchantable tubers. The selected hills are kept separate. Each 
should be given a number and should be sufficiently described to 
permit further comparison when the progeny is harvested. It will 
be found that many a promising first-year selection will bring disap- 
pointment in the second season. A few, however, will maintain their 
superiority, and these should be saved and propagated. 
This line of work has proved almost as fascinating to the writer as 
the broader one of combining desirable characters through cross- 
fertilization or hybridization. It is a field of endeavor open to any 
wide-awake potato grower and within its limitations offers greater 
promise of results for the time and effort expended than that of the 
production of seedling plants. 
Cards, the character of which is shown by the accompanying sam- 
ples, have been prepared by the writer for the purpose of recording 
i Webber, H. J. Method of improving potatoes. In N. Y. (Cornell) Agr. Exp. Sta.. Bui. 251, p. 322- 
332, 1908. 
