CHAPTER XXXI 



RUTACEiE (Rue Family) 



Description. — This family is represented by trees, shrubs, 

 and herbs. The leaves are alternate or opposite, simple or 

 compound, exstipulate, and glandular-dotted. The glands, 

 which appear as translucent dots, are internal. They vary 

 somewhat in size and shape. The flowers (Figs. 200 and 201) 

 are soHtary or in small axillary or terminal cymes. The sepals 

 are four to five in number, biit sometimes 

 absent. There are as many petals as 

 sepals, and they are either hypogynous or 

 perigynous. The separate or united 

 stamens are attached to the receptacle, 

 and vary considerably in number; the 

 anthers are two-celled, usually versatile, 

 and introrsely dehiscent. The two to five 

 carpels may be distinct, or united to form 

 a compound pistil. The receptacle is frequently modified 

 to form an annular disk (Fig. 201, B). The fruit is a capsule, 

 berry, drupe, or samara. The seeds are oblong or kidney- 

 shaped, and have a straight or curved embryo, a fleshy 

 endosperm, and fleshy cotyledons. The seeds of lemon may 

 germinate in the fruit. 



Geographical. — The family is well represented in the tropical countries. 

 There are, according to Britton and Brown, about no genera and 880 species. 

 A few members of the Rue Family are native to the United States; chief of 

 these are the prickly ash (Xanthoxylum), hop-tree (Ptelea), and torch-wood 

 (Amyris). None of the Citrus species are native of America. 

 476 



Fig. 200.— Floral 

 diagram of Citrus. 

 (After Eichler.) 



