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. 

 The multiple fleshy fruits of the Mul- 

 berries are edible, and the leaves of Mul- 

 berries constitute the food for silkworms. 

 The Hemps are well-known fiber plants, 

 and the Hop Vine is extensively grown 

 for its fruits, which are used in brswing 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, I^ield or Sheep Sorrel (Fig. 423), 

 Black Bindweed, Climbing False Buckwheat, and the Smart- 

 weeds are common ones. 



FIG. 421. Pistillate 

 flowers of the Fig, show- 

 ing the flowers borne in 

 a hollow receptacle. 



