Ch. X.] ON THE DISEASES OF WHEAT. 159 



arisen, in consequence of the extraordinary exhalations from vegetation, 

 occasioned by the increased heat. It may thus be produced by combined 

 causes in different states of the air ; or it may arise in corn, if, when un- 

 sheathing its ear, it should iiappen to rain, and to be succeeded by a frosty 

 night, for the grain will then be certainly injured in the part which is left 

 uncovered ; or if, when the corn is in blossom, and the farina just ready to 

 scatter, much cold, driving rain should happen, one side of tlie ear may 

 have all the farina washed away, or otherwise injured, while the other side 

 may he only partially so. Even a dry frost will injure it, though not so 

 materially ; but any sudden check in the progress of vegetation, whilst the 

 grain is forming, will probably exhibit a blighted or disordered ear. The 

 plants assume a pale emaciated appearance, the straw becomes spotted 

 very thick with black or grey spots, looks mouldy, and the grain becomes 

 lean and shrivelled*. 



In the present state of botanical knowledge, as it regards the diseases of 

 com, it is out of our power to offer any remedy for injuries arising from 

 such various and uncertain causes; but as they seem to be chiefly occa- 

 sioned by a close state of the atmosphere, they may be partly guarded 

 against by preserving as free a circulation as possible of air among the 

 plants, by keeping the fences as low as the security of the crops will per- 

 mit ; and especially increasing its current, by drilling the grain instead of 

 sowing it broad-cast. It has also been found, — notwithstanding what has 

 been said regarding the production of fungus, — that wheat which has been 

 recently dunged has been found more subject to rust and mildew, than that 

 which has been sown upon a clean fallov/ ; it may, therefore, be advisable 

 to check the too rapid growth of the sap, by moderating the excess of 

 manure, as strength and solidity will be tlius imparted to the straw f. 



Smut is a disease almost peculiar to the grain of wheat, the husk of which, 

 instead of containing healthy farina, is filled with a black, stinking powder, 

 rendering it unfit for the baker, and in many cases, utterly unsaleable. 

 Though distinctly known as ' Smut,' it is yet often confounded, both by far- 

 mers and naturalists, under the different names of ' Smut-bal!,' ' Pepper- 

 brand,' *• CoUibrand,' ' Brand-bladders,' 'Dust-brand,' and manv others ; but 

 it is actually occasioned by two different species of very minute substance, 

 resembling seeds, the one composed of hard grains, like those of pepper, and 

 the other of soft bladders^. It thus exhibits itself in two ways : in one, the 

 husk bursts, and the black powder is mostly dispersed by the wind and rain ; 

 and in the other, the husk remains entire, is cut, carried, and thrashed with 

 the bulk of the crop. In that state smut-balls cannot be separated from the 

 corn, and when in large quantity their offensive smell materially affects 

 the flour. 



It is generally supposed to be a fungous production ; but its history is 

 obscure, and it has not been ascertained whether it arises from a parasitic 

 plant, or is the work of an insect. That it is not a radical distemper ap- 

 pears to be admitted, else all the culms and ears from the same seed would 

 be equally affected, which is seldom the case, whole plants, and even the 

 sam.e ears, being only partially smutted, which would not happen did the 

 disorder originate in the root §. 



The real nature of the disease has hitherto eluded the researches of the 



* Malcolm's Comp. of Mad. Husb., toI. ii. p. 245, 252. 



f See A Prize Essay on the Growth of Wheat, by George Webb Hall, Esq., in the 

 Papers of the Bath Agric. Soc, vol. xv., art. 14. 

 J Papers of the Bath Aj^ric. Soc, vol. xv., art. 1. 

 § See Main's Vegetable Physioloi^y, 



