MANNA, a saccharine exudation obtained by making inci sions on the trunk of the flowering or manna ash tree, Fraxinus Ornus. The manna ash is a small tree found in Italy, and ex tending to Switzerland, South Tirol, Hungary, Greece, Turkey and Asia Minor. It also grows in the islands of Sicily, Corsica and Sardinia. It blossoms early in summer, producing numerous clusters of whitish flowers. At the present day the manna of com merce is collected exclusively in Sicily from cultivated trees. In the frassinetti or plantations the trees are placed about 7 ft. apart, and after they are eight years old, and the trunk at least 3 in. in diameter, the collection of manna is begun. This operation is performed in July or August during the dry weather, by making transverse incisions 1 to 2 in. long, and about 1 in. apart, through the bark, one cut being made each day, the first at the bottom of the tree, another directly above the first, and so on. In succeed ing years the process is repeated on the untouched sides of the trunk, until the tree has been cut all round and exhausted. It is then cut down, and a young plant arising from the same root takes its place. The finest or flaky manna appears to have been allowed to harden on the stem. A very superior kind, obtained by allowing the juice to encrust pieces of wood or straws inserted in the cuts, is called manna a cannolo.
Manna of good quality dissolves at ordinary temperatures in about 6 parts of water, forming a clear liquid. Its chief con stituent is mannitol or manna sugar, a hexatomic alcohol, which likewise occurs, in much smaller quantity, in certain species of the brown seaweed Fucus, and in plants of sev eral widely separated families. The best manna contains 7o to 8o%. It crystallizes in shining rhombic prisms from its aqueous solution and as delicate needles from alcohol. Manna possesses mildly laxative properties, and on account of its sweet taste is employed as a mild aperient for children. It is less used in England now than formerly, but is still largely consumed in South America.
The manna of the present day appears to have been unknown before the 15th century, although a mountain in Sicily with the Arabic name Gibelman, i.e., "marina mountain," appears to point
to its collection there during the period that the island was held by the Saracens, 827-107o.
Various other kinds of manna are known, but none of these has been found to contain mannitol. Alhagi manna is the produce of Alhagi maurorum, a small, spiny, leguminous plant, growing in south-western Asia. This manna occurs in the form of small, roundish, hard, dry tears, varying from the size of a mustard seed to that of a coriander, of a light-brown colour, sweet taste and senna-like odour. Tamarisk manna exudes in June and July from the slender branches of Tamarix gallica, var. mannifera, in the form of honey-like drops, which, in the cold temperature of the early morning, are found in the solid state. This secretion is caused by the puncture of an insect, Coccus manniparus. This kind of manna seems to be alluded to by Herodotus (vii. 31). Under the same name of gaz-angubin there are sold commonly in the Persian bazaars round cakes, of which a chief ingredient is a manna obtained to the south-west of Ispahan, in August, by shak ing the branches or scraping the stems of Astragalus florulentus and A. adscendens.
Oak manna or Gueze-elefi, according to Haussknecht, is col lected from the twigs of Quercus Vallonia and Q. persica, on which it is produced by the puncture of an insect during August. A substance collected by the inhabitants of Laristan from Pyrus glabra strongly resembles oak manna in appearance. Australian or Eucalyptus manna is found on the leaves of Eucalyptus vim inalis, E. Gunnii, var. rubida, E. pulverulenta, etc. The Lerp manna of Australia is of animal origin. Briancon manna is met with on the leaves of the common larch (q.v.), and bide-khecht on those of the willow, Salix fragilis; and a kind of manna was at one time obtained from the cedar.
The manna of the Biblical narrative answers in its description very closely to the tamarisk manna.
See Bentley and Trimen, Medicinal Plants (188o) ; Watt, Dictionary of Economic Products of India, under "Manna" (I8gi).