330 



On Rust, or Black Blight in IVlieat. 



Vol. IV. 



takes place : and it has been well observed, 

 that when crops intended to ripen their seed, 

 are objects of culture, there is not only 

 wanted a degree of vigour and luxuriance 

 in the plants sufficient for the purpose, but 

 if the fertility of tlie soil be raised to ?l higher 

 pitch than is necessary or consistent with 

 that object, injurious, rather than beneficial 

 consequences may be the result : land may 

 be too rich for grain crops, and it is better 

 to keep it in a well-balanced condition or in 

 a medium state of productiveness for this 

 purpose, than in too fertile a state. The 

 greater quantity of sap and juice in vege- 

 tables growing on highly cultivated lands, 

 it is evident, must necessarily render them 

 more susceptible of the effects of sudden 

 and extreme changes, and consequently, more 

 liable to disease; besides, as mushrooms 

 are produced on beds of dung, great quan- 

 tities of manure must promote the growth 

 of fungi, or parasitical plants on the crops 

 of wheat, if they are once infected — the 

 wheat produced on the site of a dunghill is 

 always rusted, even in the most favourable 

 seasons, and if the whole field is a species 

 of dunghill, how can it escape ? 



A too frequent repetition of crops of wheat, 

 more especially when accompanied by great 

 quantities of manure to force a crop, will 

 often have the same effect. The rust was 

 but little known in the western or northern 

 parts of England, or the southern counties 

 of Scotland, until of late years, when every 

 exertion has been made to increase the quan- 

 tity of that grain in those countries." 



T. A. Knight observes, " By crossing the 

 different varieties of wheat a new sort may be 

 produced, which will completely escape being 

 rusted, although crops in the neighbourhood, 

 and in almost every district in the country, 

 may suffer for it in the same year ;" and he 

 then goes on to argue, " these circumstances 

 tend to prove, that the rust does not depend 

 solely on atmospheric influence; otherwise, 

 it could not be prevented by change of seed, 

 or by the crossing of different varieties." 

 Now, this theory of Mr. Knight's is ground- 

 ed on a superficial view of things, and is a 

 mere fallacious hypothesis. Indeed, all these 

 •great naturalists appear to have bewildered 

 themselves in specious theory, and from not 

 having traced the operations of nature to its 

 source, have, throughout, mistaken the effect 

 for the cause. 



Now, suppose a farmer was to find a sheep 

 unhappily reduced, and preyed upon by mag- 

 gots, or the larva of the flesh-fly, he may 

 very justly suppose that the maggots reduced 

 the sheep, and as justly expect, that what- 

 ever sheep were subjected to the maggots 

 would be reduced in the same manner — then 

 what would be the best and proper remedy 1 



Knowing the maggots to be produced by 

 eggs deposited by flies, would he try to cover 

 his sheep from the flies, or attempt to remove 

 them where there were no flies ? Now, 

 where is the farmer or shepherd that does 

 not know that flesh-flies will not deposit their 

 eggs on a healthy part of a sheep, or if they 

 do, that they will not produce maggots? 

 they know full well, that if a sheep be dis- 

 eased by eruptions, or if wounded, the flies 

 will find out those places, and there deposit 

 their eggs; and therefore, the remedy is sim- 

 ple — cure and prevent the disease, or protect 

 the wounds, and the evil is avoided — remove 

 the cause, and the effect ceases. And very 

 similar will be found the disease in wheat, 

 called the rust, or black blight, and its cause. 

 The fungus undoubtedly preys upon that 

 which is intended to nourish and sustain the 

 wheat, but what afforded an attraction and 

 lodgement for the fungus? this is the grand 

 question. It is stated that the fungus is a 

 parasitical plant, like the misletoe, but this is 

 not the fact, for the fungus has no power to 

 attach itself to, or penetrate the healthy stalks 

 of the wheat, any more than the larva of the 

 flesh-fly have the healthy skin of the sheep. 



Any one who will examine the stalks of 

 wheat growing on a luxuriant, rank soil, 

 about the time of its first showing the swell- 

 ing of the ear, will perceive the vessels to 

 become ruptured, either from the luxuriant 

 flow of the sap upon the tender tops of the 

 plants being checked by cold winds, or an 

 unhealthy overfulness, or some other casual 

 obstruction ; and the sap being thus suddenly 

 checked, will rupture the vessels, and ooze 

 out through little slits, or longitudinal fis- 

 sures ; the discharged matter will soon as- 

 sume the appearance of a white jelly ; as it 

 dies, it will become yellow, and then brown, 

 and of a hard texture ; and in proportion as 

 the sap-vessels are injured and destroyed, 

 and this exudation takes place, the plant 

 must, of course, more or less fail in its sup- 

 ply of nourishment to the grain. In some 

 cases, the strongest stalks will not be able to 

 push the ear beyond the leaf, and the corn, 

 consequently, will be starved : and whilst 

 the season continues dry and cold, the ex- 

 uded sap will remain like dry gum ; but as 

 it advances, and the weather becomes warm 

 and moist, the gum becomes moist, soft and 

 putrefying, and then it forms and affords a 

 nutritive bed for the mould or fungus, which 

 grows and increases until it is deprived of 

 moisture, or is so reduced as to be insufficient 

 to sustain it, when it dies ; and according as 

 the season is favourable or unfavourable to 

 its growth, it produces a brown or black 

 powdery substance in a proportional quantity. 

 Thus then, the foundation or cause of the rust 

 of fungus is the putrefying matter discharged 



