306 TEXTBOOK OF BOTANY 



of them have a three-parted pistil whose ovary splits into 

 three parts in the ripe fruit. In the spurges themselves 

 (belonging to the genus Euphorbia) each small cluster of 

 flowers is surrounded by white or colored bracts that look 

 like petals ; the cluster thus is likely to be taken for a single 

 flower, but it really contains a pistillate flower consisting 

 only of a pistil, and a number of staminate flowers each with 

 one stamen and no sepals or petals. The plant known as 

 " Poinsettia " is a Euphorbia ; its showy, red, petal-like leaves 

 are bracts. Some other Euphorbias are also grown for 

 ornamental purposes. Most of the plants of this family 

 have a milky juice, from which, in the case of several species, 

 rubber is obtained. Most important is the " Para rubber " 

 furnished by two species of Hevea. The milky juice of a 

 Moroccan Euphorbia is the source of a resinous gum ; and 

 the juices of certain members of the family are poisonous. 

 Tapioca, obtained from the roots of the cassava, is an im- 

 portant food product of the tropics. Another member of the 

 spurge family is the castor-oil plant. 



321. The Vine Family. Grapes are said to have been in 

 cultivation longer than any other fruit. Those cultivated 

 in Asia and Europe belong to the species Vitis vinifera. 

 Varieties of this species are raised also in California ; some 

 are used in making wine, some for raisins, and some as table 

 grapes. Most of the grapes cultivated in other parts of the 

 United States belong to varieties that have been developed 

 from several North American species ; they are used mainly 

 as table grapes. The small fruits of a variety of Vitis vinifera 

 are dried and sold as " Greek currants." It was to these 

 fruits that the name currant was first given (from the 

 name of the Greek city of Corinth), and later it was ap- 

 plied to the fruits that we now more commonly know 

 as currants. The Virginia creeper (or woodbine), the 

 Japanese ivy, and some other climbing plants also belong 

 to this family. 



