210 PLANT ORGANS OR PARTS OF PLANTS. 



Chemistry. — The principal constituent is mucilage. 

 One part of this dissolved in thirty of hot water forms a 

 jelly on cooling. It is precipitated by alcohol and lead 

 acetate, is not colored blue by iodine, and in the pure 

 state contains no nitrogen. Boiled with nitric acid it 

 yields mucic acid. Some albuminoids are also present. 

 Fifteen per cent, of ash, mostly sulphates, phosphate, and 

 chlorides ; traces only of bromides and iodides. 



SANTONICA. LEVANT WORMSEED. 



The unexpanded flower heads of Artemisia pauci flora, 

 Weber (nat. ord. CompositcB). 



Alexandria, Aleppo, or Levant wormseed is the product 

 of a woody perennial shrub, about 6 cm. high, growing 

 abundantly in Turkestan and the steppes of southern 

 Siberia. 



Description. — The unexpanded flower heads are ovoid, 

 elongated, about 3 mm. long and i mm. thick. When 

 fresh they are yellowish-green, becoming brown with 

 age. The involucre is formed of about twelve closely 

 imbricated scales, the inferior ones very small, the supe- 

 rior internally smooth, strongly keeled and bearing many 

 small, shining, resinous glands on the outer surfaces. 

 Their margins are colorless and membranous. The flower 

 heads are separate, shining, and always smooth. This 

 characteristic distinguishes the true from inferior varieties 

 whose flower heads are rendered adherent by the presence 

 of a fine down. (Planchon and Collin.) The involucre 

 encloses upon a naked receptacle three to five unde- 

 veloped florets, each divided at the summit into five 

 triangular teeth. The odor is strongly aromatic, the 

 taste bitter and camphoraceous. 



Histology. — The epidermal cells of the involucre scales 

 are small, angular, slightly thick- walled, axially elon- 

 gated. They compose entirely the membranous scale 

 margins, but in the thick central portion they enclose 



