1a. Corolla rotate; anthers close together (flowers in summer) --2. 1b. Corolla not rotate; anthers separate --5. 2a. Stem and leaves prickly (3-8 dm. high) --3. 2b. Stem and leaves not prickly --4. 3a. Flowers white or bluish =Horse Nettle, Solanum carolinense.= 3b. Flowers yellow =Buffalo Bur, Solanum rostratum.= 4a. Climbing vine; leaves frequently lobed (flowers blue) =Bittersweet, Solanum dulcamara.= 4b. Not climbing; leaves toothed (flowers white) =Nightshade, Solanum nigrum.= 5a. Climbing or trailing shrub, with purplish, white, or greenish flowers about 1 cm. wide (frequently thorny; flowers in summer) =Matrimony Vine, Lycium halimifolium.= 5b. Herbaceous plants, not climbing --6. 6a. Flowers white, red, or blue, 2.5 cm. or more wide (summer) --7. 6b. Flowers yellow, yellowish-white, or greenish-yellow (summer) --12. 7a. Corolla-tube 10 cm. long or more (5-12 dm. high) --8. 7b. Corolla-tube 5 cm. long or less --10. 8a. Stem finely pubescent; leaves entire or nearly so =Thorn-apple, Datura metel.= 8b. Stem glabrous; leaves coarsely toothed (Jimson Weed) --9. 9a. Stem green; corolla white =Jimson Weed, Datura stramonium.= 9b. Stem purple; corolla light-blue or purple =Jimson Weed, Datura tatula.= 10a. Corolla pale-blue (5-10 dm. high) =Apple of Peru, Nicandra physalodes.= 10b. Corolla, red or violet (2-4 dm. high) =Petunia, Petunia violacea.= 10c. Corolla white --11. 11a. Corolla all white (2-4 dm. high) =Petunia, Petunia axillaris.= 11b. Corolla with yellow center =White Ground Cherry, Physalis grandiflora.= 12a. Corolla 30 mm. wide or more, somewhat irregular; stamens declined to one side (3-6 dm. high) =Henbane, Hyoscyamus niger.= 12b. Corolla smaller, strictly regular --13. 13a. Flowers in terminal panicles; corolla tubular, with slightly spreading lobes (5-10 dm. high) =Wild Tobacco, Nicotiana rustica.= 13b. Flowers solitary in the axils; corolla short, widely spreading (3-8 dm. high) (Ground Cherry) --14. 14a. Annuals with branching slender roots --15. 14b. Perennials with thickened roots and rootstocks --16. 15a. Plants pubescent =Ground Cherry, Physalis pubescens.= 15b. Plants smooth, or with a few scattered hairs =Ground Cherry, Physalis ixocarpa.= 16a. Stem viscid-pubescent =Ground Cherry, Physalis heterophylla.= 16b. Stem glabrous or slightly pubescent, not viscid --17.