158 TURNIP AND CABBAGE-ROOT ATTACKS. 



One of the most important measures, however, for keeping the 

 attack in check is securing clean ground for the crops. 



Where infested roots are left about, all the spores of the " Slime 

 Fungus " (see p. 150 for description) will be ready to start new attack. 

 In the words of Prof. Marshall Ward, p. 55 of work previously quoted, 

 " All the hundreds of thousands of them contained in the malformed 

 roots above described will be set free in the soil as the roots decay, or 

 into the manure heaps on which they may be cast to rot." 



This very important consideration is strongly urged in the following 

 note, with which I was favoured by Mr. Gilbert Murray: — "Care 

 should be taken not to use the roots affected by the disease for the 

 feeding of stock, or in any way where they can become mixed with 

 the farmyard manure, otherwise the germs of the disease are again 

 conveyed to the land, and thus perpetuates the disease you wish to 

 eradicate." 



Care also should be given to gathering up all remains of infested 

 roots on a field that has been attacked, and burning them. If they are 

 merely ploughed in, the spores will germinate, just as weed seeds might 

 germinate in similar circumstances ; and though a crop liable to injury 

 will not in common farm practice be on the land for several years, 

 there are various common weeds, and most especially Charlock, which 

 may keep the Fungus supplied with food for its successive generations 

 until the time for a crop liable to infestation, as Turnips, Swedes, or 

 Cabbage, comes round again. 



As yet we do not know on what the young Slime Fungi feed if the 

 plants which we know of as their regular food are absent from the soil. 

 In a dried state the spores will live for years. This does not apply 

 most certainly to the state of our fields, but yet from the recurrence of 

 attack there appears to be no doubt that the infestation has had some 

 congenial nourishment, even when what we recognise as such was not 

 noticed. 



To give one more quotation from Prof. Marshall Ward, which well 

 describes the progress of the affair: — " The spores lie, as we have seen, 

 in the cells of the root, like shot in a bag, and remain quiescent during 

 the winter, becoming set free into the soil as the root rots, and lying 

 there ready to germinate as before in the following spring, when their 

 progeny will have good times once more if fortune favours them in the 

 shape of new crops of plants of the Cabbage tribe. 



" What they will do if no such plants are put into the ground no 

 man knows, though it is certain many millions of them die every year. 

 It is not improbable that they can support themselves to some extent 

 as saprophytes, but this is not yet demonstrated." 



But with the knowledge that the spores (that is, the minute live 

 specks, which in plants of this nature answer to a certain extent to the 



