158 BRITISH HUSBANDRY. [Ch. X. 



tlie 20th of Julv. Should the weather, at this last-mentioned period, be 

 drv> and at a liigh temperature, no ill effects take place ; but should the 

 we'ather then set in wet, chilling the air, and checking the exhalations from 

 the ground, the straw is immediately struck, and suddenly changes from a 

 bric^ht vellow to a dingy hue, a certain sign that the blight, as it is com- 

 monly called, has seized the crop. About this time the grain is just arriv- 

 in'i- at perfection ; if the attack takes place before this is effected, it never 

 fills ; if afterwards, less damage is sustained : the straw may be injured, but 

 not the grain *." 



This description accords very closely with that of mildew ; but 

 whether considered separately, or viewed as one and the same disorder, 

 appearing at different periods of the plant's growth, both may be justly 

 ascribed to an unhealthy state of the atmosphere. Farmers are, indeed, 

 generally satisfied, that not only the extent, but the very appearance of 

 blight, rust, and mildew are entirely governed by the seasons ; and that 

 with respect to wheat, the kind sown, whether thin or thick-chaffed, has a 

 considerable effect in lessening or increasing their influence. It rarely 

 ha])pens that ihey are felt in dry, warm seasons, except in confined enclo- 

 sures or marshy ground, where the evening dews stagnate, and fogs are 

 generated ; while, on the other hand, in every moist season, whether cold 

 or warm, blight, mildew, rust, and gum on the ear, are always more or less 

 prevalent. Thus, in looking over a blighted field of wheat, we may ob- 

 serve that the lowest and richest parts, or where the crop is thick upon the 

 ground, are more affected than those which stand higher. 



Some writers have imagined that the fungus is the eff"ect, not the cause, 

 of the maladv : the evil, as they contend, proceeding from exuberant growth 

 and a surcharged state of the sap-vessels, and advise the farmer to dress the 

 ground moderately, in order to save his crop. Were the stunted plants 

 never spared, their opinion might have some weight ; but in a blighted 

 year, every plant, from the smallest to the largest, suffers. Thin-chaffed 

 wheats are also much less injured than those v,-hich are thick-chaffed, which 

 circumstance is in direct opposition to the doctrine of disease being brought 

 on by parasitical plants, or fungi. 



The same species of fungus, or one nearly allied to it, is frequently seen 

 on the common barberry bush, colt's-foot, and other plants ; and the dis- 

 ease is thus commonly supposed to be communicated to wheat. Sir Joseph 

 Banks indeed tells us, "that the village of Rollesby, in Norfolk, where bar- 

 berries abound, and wheat seldom succeeds, is called by the opprobrious 

 appellation of ' Mildew Rollesby.' A laugh has been thus raised against 

 old-fashioned farmers, who eradicate barberry from their hedges ; there is, 

 however, more propriety in the practice than superficial observers are dis- 

 posed to allow ; for as the ovae float in the air, there is no means of check- 

 in"- their attacks : and although it is said to have been lately ascertained by 

 Mr. Rennie, that the fungus is a distinct species from that observed on the 

 barberry, yet no harm can accrue from the precaution f. 



Blisiit is accounted for, as being brought on the corn by the effects of 

 very sudden changes of the weather, as during a hot sun and a still air, 

 when the atmosphere is suddenly over-charged and obscured with fog or 

 mist ; or when, after a hot day and night, tlie sun in the succeeding day 

 has not been sufficiently clear and bright to dispel the vapours which have 



* Illustrations of Vegetable Physiology, by James Main, A.L.S., p. 284. 



t Main's Vegetable Physiology, p. '^85; Farm. Mag., vol. vi. p. 225; Dumfries 

 Rep., p. 186. See also an' Account of the Barberrj-bush Fungus, with Descriptive 

 Plates, lu the Devonshire Survey, p. 438. 



