180 



INJURIOUS INSECTS AND FUNGI. 



[Sept. 1895. 



not a serious item, but the results of future experiments must 

 decide whether it is profitable or not. It can be readily under- 

 stood that lime applied in the form of a fine powder is far more 

 effective than lime put on in the ordinary way, almost as it 

 comes from the kiln, with large lumps scattered here and there 

 which are allowed to " run down " gradually from the action of 

 air and moisture. In these circumstances there is not by any 

 means an even distribution of the particles of lime, and there is 

 consequently a great waste of material. 



Dr. Soiiierville emphasizes statements that have been made by 

 other writers as to the very infectious nature of this disorder, 

 which may be conveyed in infected soil or infected roots, and 

 remarks that the main points to be observed in this connexion 

 are : — 



(a.) That no diseased roots be consumed by stock at the 

 homestead, for the fungus is thus certain to get into 

 the farmyard manure in greater or less quantity, and 

 will thus be conveyed to fields which will probably 

 be used for the cultivation of turnips. Such roots 

 should be consumed either where they grow or on a 

 permanent grass field. 



(6.) That carts or horses should on no account traverse a 

 diseased soil and afterwards go on to a sound one, for 

 the soil thus conveyed on the wheels of the carts, or on 

 the feet of the horses, will certainly contain the germs 

 of disease, and will be the means of spreading it. 



(c.) That the headlands should be carefully watched, so that 

 the disease may be stamped out by liming wherever it 

 appears. As is well known, the headlands are generally 

 more subject to the attack than any other part of the 

 field, and in working the land the horses and agricul- 

 tural implements carry away a certain amount of soil 

 at every turn, and thus spread the disease over the 

 whole field. 



{d.) That, unless conveyed mechanically, the disease is not 

 apt to spread far. In the experiments above alluded 

 to, two plots, which did not contain a single diseased 

 root, were situated within 27 inches of two plots which 

 contained only two sound roots between them, and yet 

 this small interval was sufficient to prevent the passage 

 of disease germs. 

 Experiments upon club root have been carried on during the 



past four years at the Eoyal Gardens, Kew, and the results 



were published in the Kew Bulletin of June and July 1895. 



These experiments, and the conclusions derived from them, are 



summarised in the Bulletin as follows : — 



" 1. Healthy seedling cabbages planted in soil that had two 

 years previously produced a crop of diseased cabbages, became 

 diseased. Check plants from the same batch of seed, grown in 

 sterilised soil, remained free from disease. 



