FCEXICULUM. FENNEL. 239 



cells forming the surface of the oil tubes are sharply 

 angular in outline, and, with the surrounding tissue, of a 

 dark brown color, caused by the infiltration of the resin- 

 ous contents of the oil tubes. The fibro- vascular bundles, 

 one in each rib, are composed of spiral and reticulate 

 ducts, 4 to 6 microns brOad, small, 2 to 3 microns broad, 

 much pitted tracheids, and, making up the greater por- 

 tion of the bundle, bast fibres which merge gradually into 

 the characteristically large-pored parenchyma surround- 

 ing the bundle. The endocarp is also distinctly char- 

 acteristic, made up of a single layer of narrow, oblong, 

 thin, straight- walled cells, in groups which are arranged 

 at various angles to each other, but composed individ- 

 ually of regularly parallel cells. 



Powder. — The brown angular oil tube cells and sur- 

 rounding tissues form the most conspicuous elements of 

 the powder. They are of no diagnostic value, but by 

 clearing with chloral hydrate and treating with Schultze's 

 maceration fluid, the characteristic tissues may be found. 

 These are the large-pored parenchyma cells, surrounding 

 the vascular bundles and the oblong cells of the en- 

 docarp. By treating with oil the cells of the endosperm 

 are seen to contain numerous single aleurone grains, in 

 which are found calcium oxalate crystals in angular 

 masses. (Tschirch and Oesterle.) 



Chemistry. — The essential constituent is the volatile 

 oil. This varies greatly in the several varieties of the 

 drug, both in quantity and composition. It has a 

 specific gravity of 0.90 to 0.99, is soluble in all proportions 

 of alcohol, becomes crystalline at low temperatures, 5° 

 to 10** C, owing to the separation of ancthol, pinene, 

 dipentine, fenchone, and phellandrene. The percentage 

 of anethol varies greatly. The oil of the Italian or sweet 

 fennel, esteemed for its mild flavor, probably owes this 

 quality to a lower proportion of anethol. (Fliickiger.) 



