DAIRY AND SEED IMPROVEMENT MEETINGS. 249 



of a given strain of potatoes by selection, as it is generally un- 

 derstood, 1 should be on debatable ground. However, it is a 

 w^ell-established fact that, with plants, the strains of the same 

 variety often show a marked difference in disease resistance 

 and vigor. Bearing in mind that sexual reproduction is en- 

 tirely eliminated in ordinary potato culture, it is also evident 

 that the yield on a given field is the composite result of a large 

 number of different strains, each of which is propagated year 

 after year, and which may show wide differences in produc- 

 tivity. To state the case concretely, is it not possible, when, 

 for example, an average yield of 300 bushels per acre is 

 secured on a given field, that this yield is the combined results 

 obtained from strains producing possibly anywhere from 50 

 to 500 bushels per acre? If such is the case, and there is 

 plenty of evidence, both from practical experience and experi- 

 mental work that it is, why not begin at once to eliminate the 

 drones and weaklings by the tuber-unit method, just as we weed 

 out the unproductive individuals from the dairy herd by means 

 of the Babcock milk test? 



Let me cite one experience of my own during the past sum- 

 mer in connection with our potato disease studies. From our 

 Green Mountain fields at Aroostook Farm in the fall of 191 5 

 we selected 24 hills of potatoes, all of which showed evidence 

 of mosaic disease on the foliage. Since these hills were se- 

 lected at random they were each undoubtedly the progeny of 

 individual potatoes produced in 1914. All the tubers in each of 

 these hills were cut in the usual way and planted together in 

 rows at Highmoor Farm in Monmouth last spring. The yields 

 produced this fall, when reduced to the same basis for com- 

 parison, varied from the rate of 39 to 364 bushels per acre. 



It is true that here we are working with strains which we 

 knew were abnormal and the results quoted were not the pri- 

 mary object of the experiment, but they illustrated a fact 

 which has been amply demonstrated by means of apparently 

 normal plants. They also possess real significance from the 

 standpoint of progress in the study of potato diseases — we are 

 coming to look at the subject from a new view-point. Spraying 

 and seed disinfection will doubtless always be necessary, but 

 it is becoming increasingly apparent that the squirt-gun is by 

 no means the only efBcient weapon at our disposal in this fight 

 against the enemies of our potato fields. 



