6 



On the Diseases of Wheat. 



copper, arsenic, and a variety of other materials which do not pos- 

 sess alkaline properties, it is supposed that all these solutions act 

 rather by destroying the vegetative properties of the fungi, than as 

 a means of removing them from the surface of the grains. It 

 may therefore be worth while to institute a set of experiments to 

 determine which supposition is really correct. Perhaps some por- 

 tion of the effect may be owing to the increased specific gravity of 

 the liquid ; or perhaps some portion of the solution may be im- 

 bibed by the steeped corn, sufficient to prevent the sporules of the 

 fungus from germinating within the substance of the plant; just 

 as corrosive sublimate, essential oils, and Russia-leather prevent 

 the formation of mouldiness. I may also add that the tempera- 

 ture at which the solutions are applied may be of some im- 

 portance. 



Section III. — On the Smut or Dust Brand (Uredo segetum). 



This disease is produced by another fungus, which is often 

 confounded with the last. The smut-fungus, indeed^ resembles 

 the bunt-fungus in colour and shape, but its spores are not half 

 so large, and it possesses none of that disgusting odour which 

 characterises the latter. Although this fungus is generally sup- 

 posed to attack the grain, much in the same way as the bunt- 

 fungus, only that it more thoroughly destroys it, this is not the 

 case. M. Ad. Brongniart has shown, in the ' Annales des 

 Sciences,' vol. xx., p. 121, that the smut-fungus destroys the ear, 

 by first occasioning the innermost parts of the flower to become 

 abortive, whilst the little stalks (pedicels) on which these are 

 seated swell, and become very fleshy. The fungus then con- 

 sumes the whole of this fleshy mass, and at length appears be- 

 tween the chaff-scales in the form of a black soot-like powder. 

 It is stated, however, by others, that it does not confine its attack 

 to the ear ; and though I have not myself witnessed its effects 

 on other parts^ it is described as infecting both chaff, straw, and 

 leaves. The spores, when ripe, burst through the epidermis, and 

 disperse in the form of a black powder, resembling charcoal. 

 Mr. Bauer has given figures, and an account of this fungus also, 

 in the ' Penny Magazine ' for 1833, p. 180. He there gives the 

 dimensions of the fungus, by which it appears that the diameter 

 of a spore is not more than the twenty-eight hundredth of an 

 inch. 



This disease is not so much dreaded as bunt, for two reasons ; the 

 spores have generally been dispersed before the corn is cut ; and 

 even when present in the flour they have no disagreeable odour. 

 It is sometimes, however, very injurious, by diminishing the pro- 

 duce. It is comparatively rare in wheat, but very common in 

 barley, and even more so in oats : rye does not appear to be sub- 



