514 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



purplish color. The full grown, but still green fruits are pickled in 

 brine and sent to market for table use. The olive fruit is in general 

 structure like the peach or apricot, the sarcocarp layer containing the 

 fixed oil. The endocarp or " olive stone " is not infrequently finely 

 comminuted and used as an adulterant of pepper and other spices, 

 as well as powdered drugs. Its presence is easily detected by the 

 characteristic stone cells (Fig. 64). 



Among the histological characteristics of the family, the following 

 are of some importance in distinguishing it from some of the related 

 groups. The fibrovascular bundles are of the bicollateral type. 

 The non-glandular hairs are usually peltate. Calcium oxalate is 

 secreted in the form of small acicular or prismatic crystals. The 

 tracheae usually possess simple pores only. In the mesophyR of the 

 leaves, sclerenchymatous fibers or spicular cells are frequently 

 developed. 



Manna. The dried, saccharine exudation from the stems of 

 Fraxinus Qrnus (Fam. Oleacese), a small tree indigenous to southern 

 Europe, where it is also cultivated, particularly in Sicily. Manna 

 is obtained by making transverse or oblique incisions in the bark, 

 the exudation flowing down the side of the tree, where it hardens, or 

 it is collected in special receptacles. Several commercial varieties 

 are recognized: LARGE FLAKE manna, consisting of light-colored 

 pieces 10 to 20 cm. in length; and SMALL FLAKE manna, which 

 occurs in smaller light yellowish-brown pieces. The former is pre- 

 ferred. 



Description. In irregular, 3-sided, more or less elongated pieces; 

 one side being smooth and concave; externally yellowish-white; 

 friable, somewhat waxy; internally whitish, porous and crystalline; 

 odor suggestive of maple sugar; taste sweet, slightly bitter and 

 acrid. 



Constituents. The principal constituent is mannitol (80 to 90 

 per cent), which crystallizes in colorless needles that are soluble in 

 water and sparingly soluble in alcohol; on sublimation it yields a 

 sweet, syrupy liquid, mannitan; the solutions of mannitol do not 

 ferment nor are they decomposed with dilute acids. Manna also con- 

 tains a green, fluorescent glucosidal principle, fraxin (resembling 

 aesculin), which occurs in bitter, colorless prisms that are soluble 

 in water and alcohol; dextrose, as high as 16 per cent; mucilage; 

 resin, and 1.3 to 4 per cent ash. 



Allied Products. A number of other species of Fraxinus indige- 

 nous to Europe also yield manna. The term " manna " is applied 

 to a number of exudations obtained from different sources and of 



