50 



It was first known in Scotland in 1780, but caused 

 inconsiderable harm until 1820, but of late years it has seriously 

 injured swedes and turnips in that country. Marshall speaks 

 of it as being known in Norfolk, in his Rural Economy of Norfolk, 

 written in 1790. 



In Australia, in the market gardens around Melbourne and 

 Brighton, club root is very prevalent.* In the United States 

 it is most destructive, and is considered one of the most dan- 

 gerous enemies of market gardeners, especially in Connecticut, 

 New Jersey, Rhode Island, Delaware, and the southern parts of 

 New York and Pennsylvania. 



Professor Eycleshymer, in a recent paper in the Journal of 

 Mycology, published by the United States Department of 

 Agriculture, says : " Among cabbages and, indeed, all members 

 of the genus Brassica, there seems to be no variety exempt 

 from attack. Many varieties were sown in the same soil, 

 under similar conditions, and, so far as could be determined, 

 no differences were present. From correspondence the same 

 conclusion is reached. It is claimed that the Rutabaga 

 (Swede turnip) is less liable to attack than the common 

 variety, and when sown in alternate drills with ' purple top ' 

 they produce a fair crop, while the latter is much affected." 



It was considered, and is even now considered by some, that 

 club root is caused by insects. Curtis, writing in 1841, remarks : 

 " That these malformations are occasioned by insects, I very 

 much doubt ; yet it is unquestionable that the bulk of the 

 turnips, when thus affected, are inhabited by multitudes of 

 beetles, maggots, &c. ... I therefore consider insects to 

 be, not the cause, but the effect of anbury, though their united 

 efforts combine in no small degree to the more speedy 

 dissolution of the bulbs." f 



There are larva? of several flies and beetles that infest the 

 roots of cultivated brassica?, but the injury done by them is 

 totally distinct from that of the Plasmodiopltora bmssicce. 



DESCRIPTION AND HISTORY. 



The Plasmodiophora brassicce, which causes " Club Root," 

 belongs to the group of fungus-like organisms, known a~, 

 Myxomycetes, or Slime-Fungi. Plasmodiophora means the 

 bearer of Plasmodia, which are masses, or congregations, of 

 protoplasm, with amseboid, that is to say, creeping, life-like 

 movement. From these plasmodia, spores (Fig. 7) are evolved 

 from which, in favourable conditions of moisture and tem- 

 perature, minute independent portions of i>rotoplasm esc-ipe. 

 These are able to move about by means of the cilia, or thread- 

 like appendages shown in Fig. 8. It is presumed that these 



* Bulletin of Ihe Department of Agriculture, U.S.A., No. 14, December 1891. 

 f Journal of the Hoyal Agricultural Society of England, vol. iv., 1st series. 



