APOCYNACEAE, the Dogbane Family
Herbs, with opposite simple entire leaves and regular flowers; sepals, petals, and stamens each 5; petals united; stamens attached to the corolla; ovaries 2, with a single style or stigma.
| 1a. Plant creeping or trailing; flowers blue, axillary, 2-3 cm. broad (spring) | Periwinkle, Vinca minor. |
| 1b. Plant erect or essentially so; flowers 1 cm. broad or less (4-12 dm. high) [— 2.] | |
| 2a. Corolla pinkish, about 8 mm. long by 6-8 mm. broad (early summer) | Dogbane, Apocynum androsaemifolium. |
| 2b. Corolla white or greenish, about 6 mm. long by 4 mm. broad (summer) [— 3.] | |
| 3a. Leaves petioled, acute at the base | Indian Hemp, Apocynum cannabinum. |
| 3b. Leaves sessile, rounded or truncate at the base | Indian Hemp, Apocynum cannabinum var. hypericifolium. |
ASCLEPIADACEAE, the Milkweed Family
Herbs, with simple entire leaves and regular flowers; juice usually milky; except in the first species, which is a twining vine. The flowers have an unusual structure: calyx of 5 sepals; petals 5, united with each other, and spreading or reflexed so that they conceal the calyx; stamens 5, united with each other and with the stigma to form a complex organ in the center of the flower; ovaries 2; on the back of each stamen is a colored projecting hood, which is frequently the most conspicuous part of the flower, and may be mistaken for the corolla.
| 1a. Twining vine, with dark purple flowers (summer) | Black Swallow-wort, Cynanchum nigrum. |
| 1b. Stems not twining [— 2.] | |
| 2a. Leaves whorled (3-6 dm. high; summer) (Milkweed) [— 3.] | |
| 2b. Leaves opposite or alternate [— 4.] | |
| 3a. Leaves in whorls of 4, lanceolate (flowers pink) | Milkweed, Asclepias quadrifolia. |
| 3b. Leaves in whorls of 4-7, linear (flowers greenish-white) | Milkweed, Asclepias verticillata. |
| 4a. Umbel sessile (4-8 dm. high; flowers green, summer) | Green Milkweed, Acerates viridiflora. |
| 4b. Umbel peduncled [— 5.] | |
| 5a. Leaves linear or narrowly linear-lanceolate (4-8 dm. high; flowers greenish-white, summer) | Green Milkweed, Acerates floridana. |
| 5b. Leaves lanceolate or broader (flowers in summer) [— 6.] | |
| 6a. Leaves pubescent beneath [— 7.] | |
| 6b. Leaves glabrous or nearly so [— 10.] | |
| 7a. Flowers brilliant orange (3-6 dm. high) | Butterfly Weed, Asclepias tuberosa. |
| 7b. Flowers red or purple [— 8.] | |
| 8a. Reflexed lobes of corolla merely purple-tinged (1-2 m. high) | Milkweed, Asclepias syriaca. |
| 8b. Reflexed lobes of corolla bright-red or purple [— 9.] | |
| 9a. The erect hoods of each flower about 5 mm. long (7-12 dm. high) | Milkweed, Asclepias purpurascens. |
| 9b. The erect hoods of each flower about 3 mm. long (6-10 dm. high) | Swamp Milkweed, Asclepias incarnata var. pulchra. |
| 10a. Leaves broadly rounded and almost sessile at base (flowers purplish) [— 11.] | |
| 10b. Leaves narrowed at the base, distinctly petioled (8-15 dm. high) [— 12.] | |
| 11a. Umbel solitary, terminal and erect on a long peduncle (4-8 dm. high) | Milkweed, Asclepias amplexicaulis. |
| 11b. Umbels terminal or lateral, bent toward one side (7-12 dm. high) | Milkweed, Asclepias sullivantii. |
| 12a. Corolla (not hoods) red (1-2 m. high) | Swamp Milkweed, Asclepias incarnata. |
| 12b. Corolla (not hoods) greenish (8-15 dm. high) | Milkweed, Asclepias exaltata. |
CONVOLVULACEAE, the Morning Glory Family
Twining or trailing herbs (except one species), with regular flowers; sepals 5; corolla 5-angled or 5-lobed; stamens 5, attached to the corolla; ovary superior, 2-3-celled.
| 1a. Plants with green foliage and conspicuous flowers (summer) [— 2.] | |
| 1b. Leafless brown or yellow plants, with very small flowers (Dodder) [— 7.] | |
| 2a. Style divided at the top into linear or oblong stigmas (flowers white or pink) (Bindweed) [— 3.] | |
| 2b. Style not divided at the top; stigmas sessile, capitate (Morning Glory) [— 6.] | |
| 3a. Stem erect; leaves rounded or somewhat cordate at base, not hastate or sagittate (1-3 dm. high) | Bindweed, Convolvulus spithamaeus. |
| 3b. Stem trailing or twining; leaves sagittate or hastate [— 4.] | |
| 4a. Calyx almost concealed by two large heart-shape bracts [— 5.] | |
| 4b. Bracts at base of calyx none | Bindweed, Convolvulus arvensis. |
| 5a. Leaves triangular-hastate, with sharp basal lobes | Bindweed, Convolvulus sepium. |
| 5b. Leaves oblong-ovate, the basal lobes obtuse | Bindweed, Convolvulus sepium var. pubescens. |
| 6a. Stem smooth or nearly so; ovary 2-celled (flowers white) | Wild Potato Vine, Ipomoea pandurata. |
| 6b. Stem with reflexed hairs; ovary 3-celled (flowers of various colors) | Morning Glory, Ipomoea purpurea. |
| 7a. Introduced weed, growing as a parasite on clover | Dodder, Cuscuta epithymum. |
| 7b. Native species, on various shrubs and herbs [— 8.] | |
| 8a. Flowers sessile [— 9.] | |
| 8b. Flowers distinctly pedicelled [— 12.] | |
| 9a. Sepals united below into a gamosepalous calyx [— 10.] | |
| 9b. Sepals separate from each other [— 11.] | |
| 10a. Calyx-lobes obtuse | Dodder, Cuscuta arvensis. |
| 10b. Calyx-lobes acute | Dodder, Cuscuta obtusiflora. |
| 11a. Flowers in dense rope-like twists on various species of herbs | Dodder, Cuscuta paradoxa. |
| 11b. Flowers in dense clusters on various species of shrubs | Dodder, Cuscuta compacta. |
| 12a. Tips of the petals inflexed | Dodder, Cuscuta coryli. |
| 12b. Tips of the petals erect or spreading [— 13.] | |
| 13a. Capsule depressed at the summit | Dodder, Cuscuta cephalanthi. |
| 13b. Capsule pointed at the summit | Dodder, Cuscuta gronovii. |