49 



Club Root. (Plasmodiophora brassicce.) 



(PLATE IX.) 



The excrescences and malformations of turnips and cabbages 

 are well known to all cultivators. In some cases the roots are 

 twisted in the most fantastical manner ; in others, there are 

 merely warts, or knobs, upon them. It is not only that the 

 roots are malformed, but their growth is hindered ;. and as the 

 plants are usually attacked in their early stages, the crop is 

 frequently almost entirely ruined. Specimens of distorted 

 young white turnip plants were sent in July last from a field 

 in which all the plants were similarly affected. The state of 

 these plants is accurately described by the Figures 1, 2, and 3, 

 delineated by Mr. Worthington G. Smith ; and it will be seen 

 from these that it would be almost impossible for plants thus 

 infected to yield a crop of any value. Other specimens came 

 to hand of much older plants, whose roots were forked and 

 twisted, and covered with protuberances. Some had large 

 cavities in them, in which were decaying matter, moulds, and 

 millepedes. Though there was a certain amount of food, there 

 was a very great deficiency in its quantity, and apparently in 

 its quality, though the late Dr. Voelcker, in a paper upon 

 " Anbury," in the Journal of the Royal Agricultural Society, 

 found that, " compared with sound turnips, the diseased roots 

 are much richer in nitrogen. The root which was most 

 affected by Anbury contained nearly the same proportion of 

 nitrogen which was found in the finger and toe excrescences 

 of the second root. This is more than double the quantity of 

 nitrogen which is contained in sound roots." * 



Cabbage plants attacked by this slime-fungus have gall- 

 like lumps also upon their roots, which prevent them from 

 properly developing leaves and forming hearts. In the case 

 of affected cauliflowers and broccoli, the heads are small and 

 misshapen, and sometimes only stunted leaves are produced. 



Rape, mustard, and kohl rabi are liable to be infested by 

 this slime-fungus, as well as charlock and probably other 

 cruciferous weeds. Sorauer states that in Germany it has 

 been found in Iberis umbellata, common candytuft, and 

 Matihiola incana, hoaiy shrubby stock, f Woronin, who has 

 written the most important treatise upon this slime-fungus, 

 puts the loss caused by it in 1876, in the neighbourhood of 

 St. Petersburg, at 50,OOOZ. 



* Journal of the Koyal Agricultural Society of England, vol. xx., 1st series, 

 t Handbuch der Pflanzenkrankheiten, vou Dr. Paul Sorauer. 

 I 74144 D 



