1906.] Degeneration of Potatoes. 



671 



An interesting example of the well-known tendency of 

 varieties of potatoes to deteriorate after cultivation for a 

 number of years is reported from West- 



Deg Potat a oes n ° f Phalia ' in German y * In this Province it 

 appears that the Magnum-Bonum potato 



has been the principal variety grown during the past twenty 

 or twenty-five years, the demand for this sort and its conse- 

 quent easy sale, combined with a satisfactory yield, preventing 

 farmers from employing more modern varieties or considering 

 the desirability of a change of seed. In 1905, however, the 

 cultivation of the Magnum-Bonum was a failure in nearly 

 the whole of the south-west of Westphalia. In the spring 

 the growth in many fields, particularly on wet land, was very 

 backward, with many gaps ; in the summer the plant was back- 

 ward in its development — in some places more, in some less — the 

 stalks being weak and short and the leaves small. The 

 fields, instead of having the usual appearance shortly before 

 ripening time of a thick and luxuriant growth, looked as 

 though they had been planted with different sorts — some with 

 strong-growing haulms and some with weak. The haulm of 

 the backward plants died a week to a fortnight earlier than 

 that of the healthy plants. 



When the crop was harvested, the diseased plants were found 

 to have only a few small tubers. In most cases the old seed 

 potatoes were not found shrivelled up and exhausted as when 

 the growth is unchecked, but to have become strikingly larger. 

 To what extent this apparent growth took place it is difficult 

 to say, but many farmers considered the size doubled. In 

 one case, where the seed-potatoes were carefully graded by a 

 machine, an increase of from nearly one-half to three-quarters 

 appeared to have taken place. The skin of these seed-potatoes 

 had become rough and cracked, and the eyes which had not 

 grown were shrivelled. When cut, the inside seemed of a Vitreous 

 nature, the surface being dirty white. Small cavities surrounded 

 with rusty-coloured patches were found near the few eyes which 

 had grown. 



The diminution in the crop was considerable ; enquiry amongst 

 a large number of farmers showed that it varied from about 



* Deutsche Landwirt haft lie he Pi esse, Nos. 91, 94, 95, 97, 1905. 



