THE POTATO IN BRITISH COLUMBIA. 21 



Opinions differ somewhat as to the best size of potato to select for seed. How- 

 ever, it is generally agreed that neither very small nor very large potatoes are 

 desirable to plant. Some growers prefer to select tubers from 3 to 8 oz. in weight, 

 with very satisfactory results. If growers would select enough good seed-potatoes 

 to plant a seed-plot each year, even a much greater improvement in the crop would 

 be obtained. 



The best methods employed in the selection of seed-potatoes for a seed-plot are : 

 First, hill method; second, tuber-unit method. 



In the hill method the hills are started from one seed-piece. The vigorous 

 plants are marked and at harvest-time each hill dug separately; those that bear 

 desirable tubers are saved for the next year's seed. Im the tuber-unit method single 

 tubers are selected of about 5 or 8 oz. in weight, true to variety and type. Each 

 tuber is cut from stem to seed end into quarters of equal size and the four pieces 

 planted consecutively in a unit of four hills. During the summer weak plants are 

 eliminated and at digging-time the harvested units should be put into separate bags. 

 The second year the tubers from each unit are again quartered and the units kept 

 separate. The weak hills are eliminated during the summer and at harvest-time each 

 unit is inspected carefully and the most productive, true to type and variety, saved. 

 The third season the amount of seed) preserved will be sufficient to plant a large 

 seed-plot and the selection of one or -more of the best pure lines should be made. 



In the selection of seed for seed-plots the following points must be kept closely 

 in mind: 



Fig. 12. A sack of well-graded potatocg (original). 



(1.) Select only potatoes which are true to type and variety. 



(2.) Never select seed from fields in which signs of leaf-roll, mosaic, and wilt 

 are prevalent. 



(3.) Js'ever use for seed, potatoes showing a dark ring in the stem-end. 



(4.) Discard potatoes showing any signs of scab, Rhizoctonia, etc. 



(5.) Always treat potatoes with corrosive sublimate or formalin before planting. 



Certified Seed. Every grower should aim to carry on some kind of seed- 

 improvement work. It need not necessarily be seed-selection for a seed-plot, 

 although the best results are undoubtedly obtained! by having a seed-plot and then 

 selecting seed from it for the field planting, provided the work is carried on care- 

 fully. For the majority of growers, however, the certified-seed plan which is being 

 introduced into this Province for the first time will undoubtedly serve a good pur- 



