10 THE DEPARTMENT OF AGRICULTURE. 



and distribution of the eyes vary much, not only in different varieties, but also 

 within the same variety. 



The flowers vary in colour from white through pinkish and purplish shades to 

 blue. The colour of the flower is of importance in recognizing varieties. In some 

 varieties the flowers never open. 



The fruit is a round berry known as a " potato-apple," " potato-ball," or " seed- 

 ball." It is two-celled and when normally developed is usually many-seeded. Seeds 

 are only used for propagation when new varieties are to be developed. Tubers 

 produced by seedlings are usually small the first year, normal size being reached 

 about the third year. It is commonly thought that the long propagation of the 



' 



Fig. 4. Enlargement of " lenticels " on potato (original). 



potato by tubers has resulted in a degeneration in seed production, and it has even 

 been stated that in certain varieties tuber production is inversely proportional to 

 the floral development, "the best tubers and largest yield being produced by the 

 type of plant whose flower-buds do not even swell." 



POTATO PRODUCTION. 



The following figures taken from the Year Book of the United States Department 

 of Agriculture give the yield in millions of tons of some of the most important food- 

 plants of the world. Owing to the war, figures for years 1915-19 are very incomplete 

 and have therefore been omitted. 



This table is the average for the five years 1911-15 : 



Table I. Million Tons. 



Potatoes 161.33 . 



Corn 116.50 



Wheat 115.10 



Oats 73.20 



Rye 52.16 



Barley ". 42.00 



The average annual production of potatoes was 161.33 million tons or over 

 5,000,000,000 bushels. The production of corn, wheat, and oats centred around 

 4,000,000,000 bushels. Potatoes therefore lead all other crops in total production. 

 The wheat-crop, however, has the greatest money value in the world, with potatoes 

 and corn probably ranking second and third respectively. 



Table II. is an approximate estimate of the percentage production of the world's 

 crop of potatoes as contributed by the various continents. The figures given have 



