76 SYLVA AMERICANA. 



which some species of aphides deposit upon the leaves. In 

 cultivated crops it is said to be prevented by manuring with soot. 

 4. Honeydew. Honeydew is a sweet and clammy substance 

 which coagulates on the surface of the leaves during hot weather, 

 particularly on the leaves of the oak, walnut and beach, 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 honeydew than one, regarding 

 it particularly as being an exudation, at least in the case of the 

 beech, whose leaves are, in consequence of an unfavorable wind, 

 apt to become covered with a sweet sort of glutinous coating, 

 similar in flavor to the fluid obtained from the trunk. 



It is certain, however, that saccharine exudations are found on 

 the leaves of many plants, though not always distinguished by 

 the name of honeydew ; which should not perhaps be applied 

 except when the exudation occasions disease. But if it is to be 

 applied to all saccharine exudations whatever, then we must 

 include under the appellation of honeydew the saccharine 

 exudation observed on the orange tree by M. De la Hire, 

 together with that of the lime tree which is more glutinous, and 

 of the poplar which is more resinous ; as also that of the Cistus 

 creticus, from which the resin Labdanum is collected, by means 

 of beating the shrub with leathern thongs, and of the manna 

 which exudes from the ash tree of Italy and larch of France. It 

 is also possible that the exudation of excrement constituting 

 honeydew may occasionally occur without producing disease ; 

 for if it should happen to be washed off soon after by rains or 

 heavy dews, then the leaves will not suffer. 



5. Dropsy, Plants are also liable to a disease which affects 

 them in a manner similar to that of the dropsy in animals, arising 

 from long continued rain or too abundant watering. Willdenow 

 describes it as occasioning a preternatural swelling of particular 

 parts, and including putrefaction. It is said to take place chiefly 

 in bulbous and tuberous roots, which are often found much 



