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BULLETIN No. 127. 



[August. 



in the origination of new types. But, even if artificially produced 

 fluctuations were heritable, there would be no necessity for their 

 production; for, owing to the hybrid character of the greater 

 number of potato varieties or for other reasons the natural 

 variation of seedlings is very great, even when they are the product 

 of crosses within the variety. Foreign varieties may very properly 

 be grown until they are fully acclimated; that is, until the varie- 

 ties are growing with full vigor. During the first year or two such 

 varieties seldom flower ; and even if. they do, the flowers fall more 

 quickly than they do with vigorous plants, and hybridization is ef- 

 fected with difficulty. 



There is also some doubt as to the value of bud variations, but 

 pending further investigations, we should watch for any such oc- 

 currences. Data soon to be published by the writer seem to indicate 

 that progressive mutations, that is, the appearance of an entirely 

 new character, rarely and possibly never, occur. Bud variations 

 are in nearly all cases merely the loss of a dominant character leav- 

 ing the recessive allelomorph to appear. Such variations are not 

 likely to be of great economic value. 



The selection of individual plants to be crossed is still a matter 

 of personal opinion and experiment. While we may not believe in 

 the heritability of vigor occurring as a fluctuation within a variety ; 

 still the greater ease of making crosses between vigorous plants is a 

 sufficient reason for their selection as mother plants. The latter is 

 due to the greater probability of their retaining the seed ball to its 

 maturity. 



Girard selected plants having the most luxuriant vegetation, 

 and according to T. A. Scarlett (88), the same method is practiced 

 in Scotland. We have found that there is a great difference in 

 varieties, as regards the value of luxuriant vegetation as a guide 

 in selecting high yielding plants. Large vines versus medium vines 

 gave fair results MI most cases ; but in some varieties as Manistee, 

 large vines rather indicated that excessive vegetative growth was 

 opposed to maximum tuber formation. 



TABLE 2. SELECTION OF HIGH YIELDING PLANTS BY SIZE 



