yee 



'club-root' disease 



When quite free the naked piece of protoplasm swims 

 about for a few hours by means of a thin flagellum {c), and 

 finally becomes a creeping amceba-like organism, termed a 

 myxanuEba (d). 



How long the spores can remain in the soil without germinat- 

 ing, and whether the myxamcEbae can live as saprophytes in the 



ground are unset- 

 tled points. The 

 myxamcebae, how- 

 ever, readily find 

 their way into the 

 roots of cabbages, 

 turnips and other 

 cruciferous plants 

 growing in their 

 vicinity, most pro- 

 bably by way of 

 the root-hairs. 

 After they have 

 entered the root 

 they creep from 

 cell to cell, feed 

 on the contents 

 of the latter, and 

 ultimately grow into the large plasmodia mentioned above; 

 possibly in some instances several myxamcebae coalesce to form 

 a single large plasmodium. 



Prevention and Remedy. — {a) Plants which are to be sub- 

 sequently transplanted should not be raised upon ground which 

 has previously carried a diseased crop, and seedlings showing 

 signs of clubbing should be burnt. 



All plants which after transplanting are found to be diseased 

 should be taken up completely before the affected parts decay; 

 if left until rotten, the ground becomes infected with myriads of 



Fig. 259. — A Transverse section of a portion of the clubbed 

 tissue of a cabbage root; « plasmodium; r fully developed 

 spores (enlarged So diameters) ; a two ripe spores ; 6 empty 

 spore membranes: c * swarm-spores,' or naked protoplasmic 

 contents soon after exit from b (enlarged 950 diameters) ; 

 d myxamcebae, later stage of c. 



