548 BOTANY AND PHARMACOGNOSY. 



Description. — Cylindrical, cut longitudinally into pieces 2 to 

 10 cm. long, about 5 to 7 mm. in diameter, or in irregular, some- 

 what curved or angled pieces ; very light ; externally whitish or 

 light brown, occasionally with small fragments of wood adhering; 

 consisting for the most part of parenchyma cells with thin walls 

 having numerous simple pores, and swelling perceptibly in water ; 

 fracture short; slight odor of sassafras; taste mucilaginous. 



Constituents. — The principle constituent is the mucilage, 

 which is not precipitated by alcohol ; it also contains a trace of 

 volatile oil. 



IV. FLOWERS. 



In quite a number of plants, particularly the Labiatae and Com- 

 positse, principles having medicinal and other properties occur in 

 relatively large amount in the flowers. These principles are, as a 

 rule, more or less volatile and aromatic, many of them being used 

 in perfumery and for flavoring, as well as for medicinal purposes. 



KEY FOR THE STUDY OF FLOWERS. 



I. Flower Buds. 



With a stalk and globular upper portion Caryophyllus 



Small, ellipsoidal, composite heads Santonica 



II. Expanded Flowers. 



1. Flower heads. 



A. Tubular and ligulate Aorets. 



Ligulate florets, bright yellow Arnicas Flores 



Ligulate florets, whitish Matricaria 



B. Chiefly ligulate Aorets. 



Whitish globular heads Anthemis 



2. Ligulate florets only. 



Corolla bright yellow Calendula 



III. Entire Inflorescence. 



Flowers pistillate, reddish-brown Cusso 



IV. Part of Flower. 



Petals only Rosa Gallica 



Style and Stigma Zea 



