I believe it will be found that _there are at least two sorts of honey-dew; the one a secretion from the surface of the leaf_, occasioned by one of the causes just alluded to, _the other a deposition from the body of the aphis_. Sir +J. E. Smith+ observes of the sensible perspiration of plants, that "when watery, it can be considered only as a condensation of their insensible evaporation, perhaps from some sudden change in the atmosphere. Groves of poplar or willow exhibit this phenomenon, even in England, in hot calm weather, when drops of clear water trickle from their leaves, like a slight shower of rain. Sometimes this secretion is of a saccharine nature, as +De la Hire+ observed in orange trees." "It is somewhat glutinous in the tilia or lime-tree, rather resinous in poplars, as well as in _Cistus creticus_." "Ovid has made an elegant use of the resinous exudations of Lombardy poplars, which he supposes to be the tears of Phaëton's sisters, who were transformed into those trees. Such exudations must be considered as effusions of the peculiar secretions; for it has been observed that manna may be scraped from the leaves of _Fraxinus ornus_, as well as be procured from its stem by incision. They are often perhaps a sign of unhealthiness in the plant; at least such appears to be the nature of one kind of honey-dew, found in particular upon the beech, which, in consequence of an unfavourable wind, has its leaves often covered with a sweet exudation, similar in flavour to the liquor obtained from its trunk. So likewise the hop, according to +Linnæus+, is affected with the honey-dew, and its flowers are rendered abortive, in consequence of the attacks of the caterpillar of the Ghost moth (_Phalæna Humuli_) upon its roots. In such case the saccharine exudation must decidedly be of a morbid nature."