478 ANGIOSPERMS 
Elm Family (Urticaceae). — The Elm family includes about 
1500 species of herbs, shrubs, and trees. Besides the Elms this 
family includes the Mulberries, Figs, Hemps, Hops, Nettles, 
tropical Bread Fruits and a number of others less important. 
The apetalous flowers are mostly unisexual. The flowers 
are usually borne in loose or catkin-like clusters (Fig. 420). In 
the Fig the flowers are produced in hol- 
low receptacles, which with the ovaries 
within form the well-known fleshy fruits 
of the Fig (Fig. 421). The fruits in this 
family vary much in size, form, and 
texture. In the Elms the fruits are 
winged and depend upon the wind for 
dissemination. 
The Elms are very popular shade trees, 
and their wood is used for flooring, hubs, 
barrels, sills, posts, and railroad ties. 
J The multiple fleshy fruits of the Mul- 
Fic. 421.— Pistillate  jerries are edible, and the leaves of Mul- 
Boge oF the eehoe berries constitute the food for silkworms. 
ing the flowers borne in 
a hollow receptacle. The Hemps are well-known fiber plants, 
and the Hop Vine is extensively grown 
for its fruits, which are used in br2wing beer and at one time 
were used in making bread. The Rubber Plant, so common 
in greenhouses and homes, belongs to this family and is one 
of a number of plants that yield the invaluable rubber from 
their milky juice. 
Buckwheat Family (Polygonaceae).— The plants of this 
family are mostly herbs, distinguished by their swollen nodes, 
sheathing stipules, and simple flowers in clusters (Fig. 422). 
The Smartweeds and Knotweeds, which are extremely common 
around gardens and in waste places, are well-known plants of 
this family. The fruit, in most cases, is an achene which is 
usually angled and sometimes winged. In case of Buckwheat, 
which is an important cereal crop, the starchy achene is ground 
into flour. Some of them, as the Rhubarb and Sorrel, contain 
acid in the leaves or stem. The family includes a number of 
weeds of which the Docks, Field or Sheep Sorrel (Fig. 423), 
Black Bindweed, Climbing False Buckwheat, and the Smart- 
weeds are common ones. 
