EXOGENOUS OR DICOTYLEDONOUS TLANTS. 



457 



centre, sometimes the ovules dispersed over the whole cavity of the 

 ovary, or nearly so. Capsule many-seeded. Seeds often very small, 

 with fleshy albumen and a minute embryo. — Ex. Gentiana, Frasera 

 (the American Columbo). A pure bitter and tonic principle ( Gen- 

 tianine) pervades the whole order. Gentiana lutea of Middle 

 Europe furnishes the officinal Gentian, for which almost any of our 

 species may be substituted. The above applies to the proper Gen- 

 tian Family. Obolaria differs in the imbricative aestivation of the 



corolla : as to the ovules lining the whole cavity of the ovary, this 

 is also the case in Bartonia (Centaurella, 3fichx.), and in some Gen- 

 tians. — The Buckbean is the type of the tribe MenyanthidEjK, 

 which has alternate, sometimes trifoliolate or toothed leaves, and a 

 valvate-induplicate aestivation of the corolla. 



88G. Ord. ApocynacetC {Dogbane Family). Trees, shrubs, or herbs, 

 with milky juice, and opposite entire leaves, without stipules. 

 Flowers regular. Corolla five-lobed, mostly convolute or twisted 

 in aestivation. Filaments distinct ; the anthers sometimes slightly 

 connected : pollen powdery. Ovaries two, distinct, or rarely syn- 

 carpous, but their styles or stigmas combined into one. Fruit com- 

 monly a pair of two follicles. Seeds often with a coma. Embryo 

 large and straight, in albumen. — Ex. Apocynum (Dogbane), Vinca 



FIG 1056. Flower of Gentiana angustifolia 1057. Corolla, and 1058, the. calyx, laid open. 

 1059 The pistil. 1060 Cross-section of the pistil, showing the parietal attachment of the 

 ovules. 1061. Ripe capsule of G. saponaria, rai-ed on a stipe: the persistent withering 

 corolla, &c torn away. 1062. A magnified seed, with its large and loose testa. 1063 Leaf of 

 Limnanthemum lacunosum, bearing the flowers on its petiole ! 



39 



