IMPROVEMENT OF THE POTATO. 389 



Owing to the great local differences in soil fertility and physical 

 character, this character of productiveness must be determined by 

 trial in every climate and for every soil. It is pre-eminently the 

 desired character of the grower, as all other characters are at 

 present, more or less fancy demands of the consumer, and concern 

 the grower only so far as the urgency of the demand affects the 

 price. Some of the characters that generally receive attention from 

 modern growers as conducive to, or correlative with, yield, are 

 disease resistance, character of haulm and leaf, time of maturity, 

 and length of stolons. 



The first character is well discussed in a recent publication of 

 Jones (59). In the writer's experience there is certainly a varia- 

 tion in the ability of different varieties to resist attacks of early and 

 late blight, but whether the differences noticed within the variety are 

 due to anything but a different time of infection is questionable. 

 That there are wide individual variations in respect to susceptibility 

 toward the physiological trouble, tip burn, is more apparent. 



The haulm should be vigorous, covering the ground when in 

 full growth, but upright and bushy rather than long and sprawling. 

 The meeting of the plants in the row conserves the soil moisture 

 when cultivation can no longer be given while an upright, bushy 

 haulm favors ease in the farm operations, and probably tends to 

 lessen disease infection. 



In general, varieties yield in proportion to their growing sea- 

 son, provided there is entire maturity before frost. Varieties which 

 are still green at the close of the season have large numbers of tu- 

 bers set but a great many of these fail to reach a marketable size 

 and the plant is killed while 'still containing much dry matter which 

 should have been transferred to the tubers. Length of stolon seems 

 to be a very strong variety characteristic and permanent when ob- 

 tained. The length should never exceed three or four inches, al- 

 though with 5. Commersonii, it sometimes reaches the extreme 

 length of ten feet. 



Variety characteristics which are prominent and which depend 

 almost entirely on the public taste to be of value, are those of tuber 

 shape and skin character. There are varieties possessing every pos- 

 sible shape, but they may be roughly divided into the oval and the 

 round and, if we wish to make a third class, the kidney shaped. 

 The popular shapes at present are quite flat, the short-oval-flat be- 

 ing the most desired. There may be a sufficient reason for this, as 

 Fischer (32 v. 2 p. 49) found that flat-round tubers or flat-oval 

 tubers showed a correlation with starch content. The actual reason 

 for popularity would seem to be the fact that potatoes of this shape 

 give a greater weight per measure, in which manner they are usu- 

 ally retailed. The eyes of potatoes of this type are also compara- 

 tively shallow, thereby giving less waste. 



