28 



CIRCULAR 112, BUREAU OF PLANT INDUSTRY. 



Table I. — Comparison of the stand of hop plants on 1 acre for the years 1909 to 1912, 



inclusive. 



Factors of variation. 



Productive hills 



Missing hills 



Hills having vines with no hops 



Hills having " bastard " vines 



Hills having male vines 



Total 



Stand per eenl 



Productive stand do. . 



With a perfect stand, under the system of planting followed on 

 this acre, there would be living plants in each of the 967 hills. Owing 

 to the prevalence of missing hills, however, the stand has been more 

 or less imperfect each year, as shown by the percentages given in 

 Table I. Aside from the missing hills the crop is further influenced 

 by the constant occurrence of unproductive plants. Of these, there 

 are three classes : The male plants, of which a small number is con- 

 sidered essential by American hop growers; the "bastard," or mon- 

 grel, plants, the frequent occurrence of which is restricted to certain 

 localities; and the normal female plants which from one of several 

 causes are nonproductive. When yield is considered, the non- 

 productive as well as the missing hills must be taken into account, 

 since the yield per acre is directly proportional to the number of 

 productive hills. The percentage of productive stand, by which is 

 meant the percentage of bearing hills, is an important inaex of produc- 

 tiveness, and on the acre in question tins figure shows, as may be seen 

 from Table I, that each year about one-tenth of the hills are wholly 

 unproductive. 



The records of the individual hills show some of the important 

 reasons for the variation from year to year in the number of missing 

 hills. The two chief causes of this variation are the more or less 

 successful yearly replanting and the annual occurrence of new 

 missing hills. The variation in these factors is numerically expressed 

 in Table II. 



Table II. — Annual variation in the number of replanted and missing hills of hops on 



1 acre. 



[Cir. 112] 



