224 



IMPORTANT FAMILIES OF PLANTS 



are unisexual and the plants are usually monoecious. Both 

 male and female flowers are borne on short spikes and have a 

 four-parted perianth or calyx. The white mulberry was intro- 

 duced into Europe about the middle of the fifteenth century, 

 into Mexico by Cortez in 1522 and into Virginia by James I 



Fig. 147— Fig. 



in 1619. It is extensively grown in China for the feeding of the 

 silk worm. The American mulberry produces a very good fruit 

 and the wood is very durable and seiwiceable for many purposes. 

 The elms (Ulmus Americana, American or white elm; 

 U. fulva, slippery or red elm; U. racemosa, corky elm) are 

 among our most valuable shade and ornamental trees. 



