CLASSIFICATION OF ANGIOSPERMS. 717 



perennial herb, with alternate, broadly ovate, repand, entire, tomen- 

 tose, mostly cordate leaves, the basal ones being from 30 to 45 cm. 

 long. The flowers are purplish-red or white, tubular and form 

 rather large corymbose heads ; the involucre consists of numerous 

 lanceolate, rigid, nearly glabrous bracts, which are tipped with 



FIG. 396. Burdock (Arctium Lap pa), a biennial herb with large, mostly cordate 

 leaves crowded at the base of the stems, and bearing small clusters of purplish flowers in 

 the shorter branches above. It is a common roadside weed, and well known because of 

 the burr-like fruits, consisting of the hooked tips of the bracts of the involucre. After 

 Brown. 



hooked, spreading bristles. The achenes are oblong and some- 

 what 3-angled, and the pappus consists of numerous short bristles 

 (Fig. 396). The root is used in medicine. 



The common burdock (Arctium minus) resembles A. Lap pa, 

 but is a smaller plant and is more common in the United States. 

 The heads are smaller and the inner bracts are shorter than the 



