I9i i] 



Root Tumours of Sugar-beet. 



831 



to three in number, originate from points near to the crown 

 of the root, and are attached by a comparatively small neck, 

 although during growth the tumour spreads over the surface 

 of the root, and appears to be attached to it by a broad surface 

 (see illustration). In some instances the tumours are quite 

 solid, in others they are more or less cavernous or spongy. 



This disease has been known since the year 1839, in coun- 

 tries on the Continent where beet is extensively grown, and 

 has been investigated by several independent plant patholo- 

 gists. The conclusion from their investigations is, that the 

 disease is primarily due to the conditions under which the 

 beet is grown, or, in other words, the disease is of a patho- 

 logical nature, and that neither insect nor fungus has any 

 share in causing the injury. From this it follows that land 

 that has grown a diseased crop of beet, is not infected in 

 such a way as to interfere with a future crop. At the same 

 time, it is advisable to remember that land that has proved 

 to be unsuitable for the cultivation of sugar-beet, and has 

 caused the formation of tumours, would be very likely to do 

 so on a future occasion. 



On the Continent the fact is well established that tumours 

 only develop on sugar-beet when grown on very dry, more 

 or less sandy soil, and that no trace of the disease has been 

 observed on roots grown in somewhat cold, wet, loamy soil. 

 This is said to be in accordance with the experience of Norfolk 

 sugar-beet growers. 



The tumours originate from the hypertrophy, or excessive 

 enlargement of small lateral rootlets. Roots bearing tumours 

 contain no cane-sugar, and are therefore useless for crushing 

 or for feeding purposes. The cane-sugar and invert-sugar 

 present in the normal root pass into the tumour, where the 

 former is first reduced entirely into invert-sugar. This pro- 

 duct, due to the growth and respiration of the tumour, event- 

 ually becomes broken up into carbonic acid gas and water. 



The tumours bear a superficial resemblance to outgrowths 

 on the roots of sugar-beet, caused by a fungus called 

 Urophlyctis leproides, Magnus. 



