"CLUBBING" ITS CAUSE AND REMEDIES. 383 



notwithstanding it has been commonly attributed to the 

 attacks of insects, wood ashes have from long experience 

 been recommended as the best remedial agent to be 

 applied. Thanks to Mr. Berkeley, we now know more 

 about the true cause of the disease, which is not the effect 

 of injury from insects; their presence in the tubercles 

 is, in fact, attributable to a diseased condition of the part. 

 From his investigations 1 "it appears that the peculiar 

 feature of the disease is the condensation and organization 

 of the nitrogenous matters of the root ; the whole energies 

 of the plant are arrested here, and, in consequence, the 

 leaves make no progress, and after a short time the plant 

 dies. It is highly probable that the disease arises either 

 from the abundant nitrogenized matter in the soil upon 

 which some chemical influence is exercised, either within 

 or without the plant, by the wood ashes or from the 

 defect of salts of potash. We are not in a condition at 

 present to explain what that exact influence may be, 

 but the fact of the cells being gorged in every part of the 

 root where there are not vascular bundles, with -such 

 dense masses of nitrogenized endochrome, and the preven- 

 tion of the disease by the application of wood ashes (con- 

 taining potash salts), lead us to imagine that these salts 

 are in some way requisite to prevent this accumulation, 

 by entering into new chemical combinations, and, at the 

 same time, supplying one of those ingredients which 

 abound in coleworts, and in the absence of a due propor- 

 tion of which, vegetation cannot proceed without disturb- 

 ance/' The accompanying woodcut, taken from Mr. 

 Berkeley's sketches, shows the different forms the roots 

 assume under the influence of this disease. In one or 

 two cases only, he says, the most careful search has 

 detected the presence of larvae, which appear, therefore, 

 to have nothing to do with the production of the malady. 



1 For details, see Agri. Gaz., 1856, p. 500. 



