A specimen furnished to Ludwig[1528] by Haussknecht afforded much mucilage, a small amount of starch, about 48 per cent. of dextrogyre grape sugar, with traces of tannic acid and chlorophyll.
Briançon Manna—This is a white saccharine substance which, in the height of summer and in the early part of the day, is found adhering in some abundance to the leaves of the larch (Pinus Larix L.), growing on the mountains about Briançon in Dauphiny. It was formerly collected for use in medicine, but only to a very limited extent, for it was rare in Paris in the time of Geoffroy (1709-1731), and at the present day has quite disappeared from trade, though still gathered by the peasants. A specimen collected for one of us near Briançon in 1854, consists of small, detached, opaque, white tears, many of them oblong and channelled, and encrusting the needle-like leaf of the larch; they have a sweet taste and slight odour.[1529] Under the microscope they exhibit indistinct crystals.
Briançon manna has been examined in 1858 by Berthelot, who detected in it a peculiar sugar termed Melezitose, answering to the formula C₁₂H₂₂O₁₁ + OH₂.
Several other saccharine exudations have been observed by travellers and naturalists; we shall simply enumerate the more remarkable, referring the reader for further information to the original notices.
Pirus glabra Boiss. affords in Luristan a substance which, according to Haussknecht, is collected by the inhabitants, and is extremely like Oak Manna. It is stated by the same traveller that Salix fragilis L., and Scrophularia frigida Boiss., likewise yield in Persia saccharine exudations. A kind of manna was anciently collected from the cedar, Pinus Cedrus L.[1530] Manna is yielded in Spain by Cistus ladaniferus L.[1531] Australian Manna, which is in small rounded, opaque, white, dry masses, is found on the leaves of Eucalyptus viminalis Labill. It contains a kind of sugar called Melitose,[1532] has a sweet thistle, is devoid of medicinal properties and is not collected for use.[1533]
The substance named Tigala (corrupted into Trehala), from which a peculiar sugar has been obtained,[1534] is the coccoon of a beetle, and not properly a saccharine exudation.[1535]
The Lerp Manna of Australia is also of animal origin.[1536] It consists of water 14, white thread-like portion 33, sugar 53 parts. The threads possess some of the characteristic properties of starch, from which they differ entirely by their form and unalterability even in boiling water. Yet in sealed tubes, they dissolve in 30 parts of water at 135° C. The sugar is dextrogyre; it impregnates the threads as a soft brown amorphous mass. In the purified state it does not crystallize, even after a long time. By means of dilute sulphuric acid, the threads are converted into crystalline grape sugar.
OLEUM OLIVÆ.
Olive Oil; Salad Oil; F. Huile d’Olives; G. Olivenöl; Baumöl; Provencer Oel.
Botanical Origin—Olea europæa L., an evergreen tree,[1537] seldom exceeding 40 feet in height, yet attaining extreme old age, abundantly cultivated in the countries bordering the Mediterranean, up to an elevation of about 2000 feet above the sea-level.[1538] Olea ferruginea Royle (O. cuspidata Wallich), a tree abundant in Afghanistan, Beluchistan and Western Sind, has been supposed to be a wild form of O. europæa, but is regarded by Brandis[1539] as a distinct species. It is not known to have been ever cultivated, yet its fruit, which is of a small size and but sparingly produced, is capable of affording a good oil.