Take-all and Whiie-hexid-s in Wheat. 415 



view, altliougli it Avas contended that the soil in large paddocks is veiy 

 variable, and that the deficiences occurred where the take-all patches 

 existed. This is very like begging the question, and goes on the 

 assumption that no manure was applied to make up for these supposed 

 deficiencies. But during this season at least, the disease appeared 

 where phosphatic manures had been applied, and the seed had been 

 drilled in, as wtU as where there was no manure. 



Third, nematode worms are often found associated with the 

 disease, and the. assumption was that they were a contributing cause, 

 but it is seen on close investigation, that while these eelworms are 

 undoubtedly present, they only appear in small numbers when decay 

 has already been set up by the fungus, and are to be regarded as an 

 accompaniment rather than as a cause of the disease. The appearance 

 presented by the attacked ])lants is suggestive of this agency, and Mr. 

 Smith, of Horsham, writing to me on the subject, remarks — " Whether 

 they have anything to do with take-all I cannot say, but the roots of 

 plants affected all a])pear to be eaten off short, say about two inches 

 from the stems." Tlais has already been referred to as a symptom 

 of the disease, and is the result of the action of the fungus 

 which causes the decay of the roots, so that when the plants are 

 pulled up, if the ground is at all firm, the roots break oft" short. 



Fourth, farmers often point to certain weeds as being the cause 

 of take-all, and although quite a number have been thus regarded, a 

 very common one is the so-called hunger plant (Silene gallica.J This 

 is a case of association and nothing more, and since such plants are 

 often found accompanying the disease, they are hastily set down as 

 the cause of it. The addition of manure, such as superphosphate, Avill 

 enable the wheat-plant to outstrip and overcome the weeds, though in 

 some cases, no doubt, the w^eds are merely there because -the death 

 of the wheat-plants gave them room to grow. 



The ground is now clear for the consideration of the cause which 

 explains all the facts, and shows the various theories in their proper 

 light. 



Disease Caused by a Fungus. 



Before intelligent measures can be taken to cope with any disease, 

 it is necessaiy to know something of the cause or causes which 

 produce it, and then one is in a position to devise means whereby the 

 cause may be removed, or if that is not practicable, to minimize its 

 injurious action as much as possible. In some instances the farmer in 

 the course of his practice, without any knowledge of the real cause,, 

 may hit upon something which counteracts its effects, and as we shall 

 see this has actually been done in the present case, but nevertheless, 

 it remains true that a knowledge of causes and the effects they produce, 

 puts us in the way of controlling them intelligently and eff'ectively, 

 and without long and laborious and often fruitless groping in the dark. 



It is not sufficient however to find a fungus associated with a 

 disease, in order to be sure that it is the cause of the mischief, for it 

 may be there simply as a scavenger to prey upon the decayed or 



