188 ELEMENTS OF BOTANY. 



gymnostegium and the nearly straight horn ; follicles ovate-lanceo- 

 late, seeds comose. April-May. Dry pine barrens. 



4. A. PEREXxis Walt. Thin-leaved Milkweed. Stem erect, 

 branched, slender, shrubby at the base, pubescent in lines above, 1-3 

 ft. high ; leaves opposite, petioled, thin, lanceolate to oblong-lanceo- 

 late, tapering at each end, smooth, pale beneath ; umbels few, long- 

 peduncled, often corymbose ; pedicels slender, shorter than the 

 peduncles ; flowers small, white ; hoods erect or spreading, about the 

 length of the gymnostegium and half the length of the erect, needle- 

 shaped horn; follicle erect, ovate-lanceolate, smooth, seeds ^ in. 

 long, without coma. May-July. On river banks and in muddy 

 places. 



II. VINCETOXICUM. 



Perennial ; stems twining ; leaves opposite, cordate, petioled ; 

 flowers in axillary umbels or corymbs; calyx 5-parted, the 

 lobes spreading ; corolla rotate, the tube very short, the lobes 

 convolute in the bud ; crown an entire or lobed ring, adnate 

 to the throat of the corolla ; stamens inserted in the base 

 of the corolla, not appendaged; gymnostegium flattened, 

 depressed; follicles inflated, smooth or armed with soft 

 spines, seeds comose. 



1. V. GOxocARPOS Walt. Large-leaved Vixcetoxicum. 



Stem slender, smooth or pubescent, twining high, 10-20 ft. long; 

 leaves ovate, abruptly acuminate at the apex, deeply cordate at the 

 base, 3-6 in. long ; petioles 1-4 in. long ; umbels peduncled, several- 

 flowered ; pedicels stout, spreading ; flower buds conic ; corolla green- 

 ish-purple, lobes lanceolate, obtuse, 3-4 times as long as the calyx, 

 pubescent within ; crown many-lobed ; follicles smooth, 3-5-angled, 

 3-4 in. long. June-August. In moist thickets. 



2. V. Carolixexse (Jacq.) Britt. Carolixa Vixcetoxicum. 

 Stem slender, hirsute, twining, 8-15 ft. long; leaves OA^ate, acumi- 

 nate at the apex, dee2:>ly cordate at the base, 3-7 in. long ; petiole 

 2-4 in. long ; umbels on peduncles as long as the petioles, 6-8- 

 flowered ; flower buds ovate ; corolla dark purple, the 'oblong lobes 

 puberulent without, smooth within ; crown 5-lobed Math a 2-cleft 

 tooth in each sinus; follicles warty. May-fJuly. In woods. 



105. CONVOLVULACEiE. MORXING-GLORY FAMILY\ 



Annual or perennial herbs ; stems usually twining or trail- 



in; 



sometimes erect ; leaves alternate, simple, exstipulate 



