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A TEXTBOOK OF THEORETICAL BOTANY 



is the source of Storax, a resin much used in ancient times, while S. benzoin 

 which occurs in Sumatra yields the fragrant Gum-benzoin which is used 



Styi ii\ jiipdtiicd. I'lowcnng shoot. 



medicinally and in the manufacture of incense. It is obtained from cuts in 

 the bark. 



The family Symplocaceae includes only one genus, Symplocos, which 

 is separated on account of the inferior ovary. There are some 300 species 

 with their centre of distribution in India; thirteen species are found in 

 New Caledonia. 



PRIMULALES 



The Primulales are Metachlamydeae in which the flowers may be either 

 unisexual or bisexual. Both calyx and corolla are pentamerous. There are 

 usually five epipetalous stamens. The ovary is superior, or rarely inferior, 

 and unilocular. The ovules are indefinite in number and are either attached 

 basally or exhibit free-central placentation. The seeds are small with a 

 straight embryo surrounded by endosperm. 



The plants are herbs, shrubs or trees with simple entire leaves. 



The limits of the order are uniformly interpreted. According to 

 Engler there are three families, of which one, the Theophrastaceae, contains 

 about seventy species confined to the tropical regions of America. The 

 second family, the Myrsinaceae, is also tropical and subtropical in distribu- 

 tion. It contains about 1,000 species, but few of them can lay claim to any 

 special importance, except Aegiceras majiis, a common mangrove tree, and 

 Ardisia crenata, which harbours colonies of nitrogen-fixing bacteria in its 

 leaves. The third family is the Primulaceae which we shall consider in 

 detail. 



