and protection of ants increase much more rapidly in numbers than those which are not attended by them.
The term honey-dew should be rigidly restricted to the sweet excretions of insects feeding on plants. Nectar is the secretion of nectaries, whether floral or extrafloral. Many plants have extra-floral nectaries on the flower stalks, leafstalks, and stipules, as cotton, vetch, passion flower, almond, peach, cherry, jewelweed, cowpea. field bean, and partridge-pea, which secrete nectar in large or small quantities. This nectar does not differ from floral nectar, as is attested by the chemical analyses of the honey of cotton gathered from both kinds of nectaries. It should never be called plant honey-dew.
It has been asserted by many beekeepers and not a few botanists in the past, that there is a third sweet liquid which, under favorable weather conditions, is exuded directly by the leaves of certain deciduous-leaved trees and shrubs, as basswood, maple, and oak. Gaston Bonnier has been frequently quoted to the effect that he had often seen trees, on which there was not a single plant-louse, covered with a sweet liquid which exuded from the leaves. Many similar views might be given. But in the majority of cases it has been conclusively shown that the sweet liquid found on the foliage of trees is of insect origin, and that the assertions to the contrary were based on insufficient observation and superficial investigation.
But a variety of sugars or mannas are yielded by a number of trees both in natural and artificial ways. Recent investigations by Davidson and Teit show that from tips of leaves of the Douglas fir in British Columbia, and Washington State, west of the Cascades, there is exuded a sweet liquid in large quantities. By the evaporation of the water it crystallizes quickly into white masses1/4 inch to 2 inches in diameter. This solid again may be dissolved by rain and recrystallized in patches at the base of the tree. “Fir sugar” was known to the Indians of British Columbia long before the discovery of America, and in recent years its presence has repeatedly been reported by beekeepers. But it does not occur every year. The sugar-yielding firs (Pseudotsuga Douglasii) are confined chiefly to the very dry belt of British Columbia between the parallels of latitude 50 and 51 degrees and the meridians of longitude 121 and 122 degrees. The sugar is not found on trees in the dense forests, but only on those in the comparatively open areas, on gentle slopes facing east and north, during hot summer droughts. In leaves of the Douglas fir exposed to continuous sunlight a larger quantity of carbohydrates is formed during the day than can be stored or carried away to the growing tissues. In the hot dry atmosphere evaporation ceases and the leaves become gorged with water, which is forced out through their tips. A beekeeper at Victoria states that many of the firs, particularly the isolated trees, are well spattered with the exudation, and the needlelike leaves studded with pale-amber diamonds. A large number of bees gather the liquid, and in some years two or three supers of sections are filled with it. The honey is fair in quality, pale amber in color, with rather dark cappings.
A beekeeper living in the Olympic National Forest, Oregon, 21 miles from Port Angeles, reports that his bees stored 150 pounds of fir sugar during a very dry season. The following winter many bees died from dysentery, which was attributed to the effects of the sugar. This seems very probable, as the composition of this excretion is very different from that of floral honey. It contains, among other constituents, nearly 50 per cent, of the rare sugar melezitose.
It is certainly not improbable that other species of conifers may, under special climatic conditions, exude a sweet liquid. In Switzerland about 40 per cent, of the honey crop is gathered from the weisstanne (Picea excelsa), a fir tree. From an excretion found on the leaves of this fir tree the beekeepers in the Vosges Mountains, the Black Forest, and in parts of Switzerland, harvest large crops of wald-honig (forest honey). J. A. Heberle believes that this honey is of plant origin,