CASUALTIES OF VEGETABLES. CHAP. XII. 



a Fungus of great minuteness, the Mucor ErisypJic 

 of Linnaeus ; or by a sort of whitish slime which 

 some species of aphides deposit upon the leaves.* 

 In cultivated crops it is said to be prevented by 

 manuring with soot* 



SUBSECTION IV. 



Honey-dew. Honey-dew is a sweet and clammy 

 substance which coagulates on the surface of the 

 leaves during hot weather, particularly on the leaves 

 of the Oak-tree and Beech, and is regarded by Mr. 

 Curtis, who wrote a paper on the subject, as being 

 merely the dung of some species of aphides.^ This 

 seems to be the opinion of Willdenow also, % and it 

 is no doubt possible that it may be the case in 

 some instances or species of the disease. But Sir 

 J. E. Smith contends that it is not always so, or 

 that there are more species of honey-dew than one, 

 regarding it particularly as being an exudation, at 

 least in the case of the Beech, whose leaves are, in 

 consequence of an unfavourable wind, apt to become 

 covered with a sweet sort of glutinous coating, 

 similar in flavour to the fluid obtained from the 

 trunk.^ 



It is certain, however, that saccharine exudations 

 are found on the leaves of many plants, though not 



* Piincip. of Bot. p. 343. f Lin. Trans, vol. vi. 



J Princip. of Bot. p. 343. Introd. p. 1S9- 



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