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 of parenchyma cells with slightly lignified walls, having 

 simple pores, and swelling perceptibly in water (Fig. 326) ; 

 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 Labiatge and Com- 

 positge, 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 ligulatc florets. 



Ligulate florets, bright yellow Arnicse Flores 



Ligulatc florets, whitish Matricaria 



B. Chiefly ligulate florets. 



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 



