712 A TEXT-BOOK OF BOTANY. 



which have been given the rank of famiHes. This division is 

 based especially on the characters of the stamens. In a small 

 group represented by the ragweed and known as the Ambrosi- 

 ACE.^, the anthers, while close together (connivent) , are not united, 

 and the corolla in the marginal or pistillate flowers is reduced to a 

 short tube or ring. In a large group, which includes probably 

 10,000 species and which is considered to be the CoMPosiT.^i: 

 proper, the stamens in the tubular flowers are syngenesious and 

 the marginal or ray-flowers are distinctly ligulate. This group 

 includes the daisy, sunflower, golden-rod, aster, thistle, and most 

 of the plants which yield official drugs. 



It may also be added that the Compositae is considered to be 

 the highest and youngest group of plants. 



Taraxacum officinale (Dandelion) is a perennial, acaulescent 

 herb with milky latex; oblong-spatulate, pinnatifid or runcinate, 

 decurrent leaves, and with a i -headed scape, the stalk of which is 

 hollow. The flowers are ligulate, golden-yellow and numerous ; 

 the involucre consists of two series of bracts, the inner one of 

 which closes over the head while the fruit is maturing, afterward 

 becoming reflexed. The fruit consists of a loose, globular head 

 of achenes, each one of which is oblong-ovate and with a slender 

 beak at the apex which is prolonged into a stalk bearing a radiate 

 tuft of silky hairs, which constitute the pappus. The root is fusi- 

 form and usually bears at the crown a number of branches 2 to 5 

 cm. long, having a small pith and other characters of a rhizome. 

 The root is official. 



Lactuca virosa (Poison lettuce) is a biennial prickly herb, 

 with milky latex and oblong-obovate, spinose-toothed, runcinate 

 basal leaves and with alternate, somewhat sessile or auriculate, 

 scattered stem leaves, the apex and margin being spinose. The 

 flowers are pale yellow and occur in heads forming terminal pani- 

 cles. The involucre is cylindrical and consists of several series 

 of bracts. The flowers are all ligulate and the anthers are sagit- 

 tate at the base. The achenes are flattish-oblong, and the pappus, 

 which is raised on a stalk, is soft-capillary, as in Taraxacum. 

 The prepared milk-juice is official as Lactucarium. 



Eupatorium perfoliatum (Boneset or Common thorough wort).. 

 ^-The leaves and flowers are used in medicine. 



