ROYAL BOTANIC GARDENS, KEW. 



BULLETIN 



0* 1 



MISCELLANEOUS INFORMATION, 



No. 8.] 



[1907. 



XLIX.-PLANT DISEASES. -VIII. DEGENERATION 



IN POTATOES. 



(With Plate.) 



G. Massee. 



During the past few years many inquiries have been addressed 

 to Kew as to the reason why potato tubers fail to form sprouts at 

 the proper season, even when placed under the most favourable 

 conditions for doing so. Last spring one correspondent stated that 

 out of 70 tons of potatoes of high grade, especially intended for 

 " seed," only five tons showed signs of sprouting, the remainder 

 being disposed of, at a serious loss, for culinary purposes. This 

 condition of things is not confined to this country. in 

 Germany («) serious losses have been sustained owing to th« 

 sterility of potato " sets," more especially of the kind known as 

 Magnum Bonum. Very few of the eyes produced sprouts, and 

 the "sets " at the time of lifting were not shrivelled and dried up 

 as is the case under normal conditions, but on the other hand 

 were solid and quite firm and in many cases had actually increased 

 in size. In one instance where the " sets " were graded by a 

 machine before planting, an increase in size of from one-half to 

 three-quarters hid taken place. This proves that the " sets " after 

 planting had commenced growth a second season, and had accumu- 

 lated the starch formed by the scanty amount of foliage produced. 

 The new tubers formed "by such plants were small and few in 

 number. In many instances sprouts were not formed, and the 

 " sets " remained intact in the soil throughout the season. The 

 loss on the potato crop varied from about 5 per cent, to total loss, 

 and averaged from 50 to 60 per cent. Investigations made by 

 Dr. Schleh and Dr. Speikermann proved the absence of any 

 specific disease, and the failure was in part attributed to the 

 practice of growing the same kind of potato from sets produced 

 on the spot for a long period of time. 



In France Dr. Delacroix (6) has described the occurrence, on a 

 large scale, of a similar sterility of potato tubers, which he calls 



1375 Wt87 8/07 D&S 29 29357 



