250 FAMILIES OF FLOWERING PLANTS. 
of the plants are troublesome weeds. Thus the genus Hieracium or 
hawkweed,. 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 (4. praealtum) and the orange 
hawkweed (ZH. 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 juncea). 
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 artemisiaefolia) may be taken as 
typical. (Fig. 220.) This plant, with its habit of overrunning every 
S bit of waste land to the exclusion of all 
other plants, would be sufficiently 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 they 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 
NV) % species at 10,000, and the family is 
FIG. 220. Ragweed (Ambrosia artemisiaefolia), distributed over all parts of the 
After Britton and Browg, II, Fl. Baie ee US. world, though as a rule less abun- 
dant in tropical than in temperate regions. 
The first two tribes in the family consist of the iron-weeds (Vernonia), 
the bonesets (Hupatorium) 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 (Hupato- 
rium perfoliatum), which furnished the thoroughwort tea of our child- 
hood days. (Fig. 222.) The tribe Astereae contains two of our largest 
