250 



FAMILIES OF FLOWEEING PLANTS. 



of the plants are troublesome weeds. Thus the genus Hieracium or 

 liawkweed, represented in this country by about 30 species, none of 

 which are very troublesome, embraces no fewer than 250 species of the 

 Old World ; and of these the king-devil {H. praealtum) and the orange 

 hawkweed {H. aurantiacum) have become serious pests to the farmers 

 in many parts of New England and New York. In Maryland and the 

 District of Columbia another European immigrant has become trouble- 

 some, the gum succory {Chondrilla jiincea). 



The ray flowers of the Chicory family are for the most part yellow, 

 but the chicory itself has blue flowers, and there are other genera with 

 white, pink and red rays. 



Family Ambrosiaceae. Ragweed Family. In this group the same 

 floral structure prevails, except that the plants are monoecious or dioe- 

 cious, and the pistillate head of flowers is frequently larger and nut-like 

 or bur-like in appearance. The corolla is reduced to a mere ring or 

 tube in the pistillate flowers ; in the staminate it is tubular and 4-5- 

 lobed ; there is no flat or expanded portion corresponding to the rays of 

 the Cichoriaceae. The ovary is inferior. There are 8 genera and about 

 55 species, largely American. The great bulk of them are pestilential 

 weeds, of which the ragweed {Ambrosia arteniisiaefolia) may be taken as 

 typical. (Fig. 220.) This plant, with its habit of overrunning every 



bit of waste land to the exclusion of all 

 other plants, would be sufiiciently dis- 

 agreeable under any circumstances ; 

 but when we reflect that it is a dis- 

 turbing factor, if not a primary 

 cause, of the disease knows as hay 

 fever, it must be accounted a vege- 

 table pariah, to be combated and 

 uprooted wherever it occurs. The 

 cocklebur {Xanthium) is also trouble- 

 some on account of the propensity 

 of its prickly burs to adhere to every- 

 thing with which thev come in con- 

 tact (Fig. 221). 



Family Compositae. Thistle or 

 Composite Family. This family is 

 the largest in the whole series of 

 flowering plants,of which it comprises 

 about eight or nine per cent. The 

 genera are estimated at 775, the 

 species at 10,000, and the family is 

 Fig. 220. Ragweed (.i^A..>5/a a.f.m«a.>M. distributed ovBr all parts of the 



After Britton and Brown, 111. Fl. Northeast. U.S. -^orld, tllOUgll aS a rule leSS abun- 

 dant in tropical than in temperate regions. 



The flrst two tribes in the family consist of the iron-weeds ( Vernonia), 

 the bonesets {Eupatorium) and their relatives. They contain nearly 

 1,000 species, dispersed throughout temperate and tropical climates. 

 A good example is furnished by the common native boneset {Eupato- 

 ruim perfoliatiim), which furnished the thoroughwort tea of our child- 

 hood days. (Fig. 222.) The tribe Astereae contains two of our largest 



