ILLUSTRATED FLORA. 



Vol. hi. 



Family 17. APOCYNACEAE Lindl. Nat. Syst. Ed. 2, 299. 1836. 



Dogbane Family. 



Perennial herbs, shrubs, vines, or some tropical genera trees, mostly with an 

 acrid milky juice, with simple opposite alternate or verticillate exstipulate 

 leaves, and perfect regular 5-parted cymose solitary or paniculate flowers. 

 Calyx inferior, persistent, the lobes imbricated in the bud. Corolla gamopeta- 

 lous, its lobes convolute in the bud and often twisted. Stamens as many as the 

 lobes of the corolla, alternate with them, inserted on the tube or throat; anthers 

 linear-oblong, or sagittate, 2-celled ; pollen-grains simple, often glutinous. 

 Ovary superior, or its base adherent to the calyx, of 2 distinct carpels, or 

 i-celled, with 2 parietal placentae, or 2-celled; ovules few or numerous, anatro- 

 pous or amphitropous; style simple, or 2-divided; stigma simple. Fruit usually 

 of 2 follicles or drupes. Seeds often appendaged by a coma; endosperm fleshy, 

 not copious; embryo straight; cotyledons flat or concave; radicle terete, usually 

 shorter than the cotyledons. 



About 130 genera and 1050 species, very widely distributed, mostly in tropical regions. 

 Leaves alternate; erect herbs. 1. Amsonia. 



Leaves opposite; vines or herbs. 



Flowers large, axillary, solitary. 2. Vinca. 



Flowers small, cymose. 



Erect or diffuse herbs; corolla campanulate. 3. Apocynum. 



High-climbing vines; corolla funnelform. 4. Trachelosperrmim. 



i. AMSONIA Walt. Fl. Car. 98. 1788. 



Perennial herbs, with alternate membranous leaves, and rather large blue or bluish flow- 

 ers, in terminal thyrsoid or corymbose cymes. Calyx 5-parted, the segments narrow, acumi- 

 nate. Corolla mostly salver-form, the tube cylindric, but somewhat dilated at the summit, 

 villous within, the lobes convolute in the bud. Stamens inserted on the throat of the corolla, 

 included; anthers ovate or oblong. Disk none. Ovary of 2 carpels, connected at the top by 

 the filiform style; ovules in 2 rows in each cavity, numerous; stigma appendaged by a re- 

 flexed membrane. Fr*uit of 2 erect cylindric several-seeded follicles. Seeds cylindric or ob- 

 long, obliquely truncate at each end, not appendaged. [Named for Charles Amson of South 

 Carolina.] 



About 8 species, natives of North America and eastern Asia. Besides the following, 5 others 

 occur in the southern and southwestern United States. 



i. Amsonia Amsonia (L,.) Britton. 

 Amsonia. (Fig. 2893.) 



Tabernaemontana Amsonia L. Sp. PI. Ed. 2, 308. 



1762. 

 Amsonia Tabernaemontana Walt. Fl. Car. 98. 1788. 

 A. Amsonia Britton, Mem. Torr. Club, 5: 262. 1894. 



Glabrous or nearly so, simple, or branched 

 above, 2-4 high. Leaves ovate, ovate-lanceo- 

 late or lanceolate, entire, acuminate at the apex, 

 narrowed at the base, sometimes pubescent be- 

 neath, 2 / -5 / long, Yz'-i' wide; petioles 2 // -4 // 

 long; flowers thyrsoid-cymose, numerous; pedi- 

 cels bracteolate at the base; calyx about \" 

 long, its segments subulate; corolla 6 // -o/ / long, 

 beaked by the convolute limb in the bud, its 

 lobes linear and about as long as the tube; fol- 

 licles 2 / -4 / long, about 2 // thick, attenuate at 

 the apex, glabrous; seeds papillose. 



In moist soil, southern Pennsylvania to Illinois 

 and Kentucky, south to Florida, Missouri and 

 Texas. v April-July. 



