POTATO BREEDING AISTD SELECTIOjS". 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 IVIETHODS. 



TUBER-UNIT METHOD OF SELECTION. 



A metliod advocated by Webber,^ known as the tuber-unit method 

 of selection, has recently received considerable attention. This 

 method consists ia plantmg 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 thau 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 seciu'ed 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, varpng 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 fii'st-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 emleavor open to luiy 

 wide-awake potato grower and within its limitations offers greater 

 promise of results for the time and effort expended thiin thsit of the 

 production of seedling pluiils. 



Cards, the chararlcr of which is shown })y t.he accompanying sajii- 

 ples, have been prepared by the writer for the purpose of recording 



» Webber, H. J. Methorl of Improving potatoes. Jn N. Y. (Cornell) Agr. Exp. Kta., Hiil. 251, p. 322- 

 182, lOOK. 



