50 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



45. Fruit a 1-seeded achene or utricle (46) . 



46. Flowers subtended by an involucre (this campanulate, 

 turbinate, or cylindric, and several-toothed or -cleft, 

 or consisting of a single 2-lobed bract) , or, if without 

 an involucre, then the stipules present and united 

 into a sheath around the stem; fruit an achene, usually 

 triangular but sometimes, in genus Polygonum, 



lenticular 33. Polygonaceae. 



46. Flowers not subtended by an involucre or this con- 

 sisting of a pair of appressed bracts; stipules none, or 

 not united in a sheath ; fruit not triangular (47) . 

 47. Stipules present; flowers perfect, in axillary clusters: 

 plants small, with spreading, prostrate, or densely 



cespitose stems 40. Caryophyllaceae. 



47. Stipules none; flowers perfect or unisexual (48). 



48. Bracts and perianth not scarious; plants often 

 fleshy, scurfy, or mealy; filaments separate. 



34. Chenopodiaceae. 



48. Bracts and perianth usually scarious; plants not 



fleshy, scurfy, or mealy; filaments commonly 



more or less united 35. Amaranthaceae. 



Series 2. Polypetalae 



Key to the families 



1. Corolla distinctly irregular (2). 



2. Leaves compound, rarely reduced to a single leaflet (3). 



3. Sepals 2; corolla conspicuously spurred, not pealike; leaves decompound 

 with numerous narrow segments, glaucous; plants herbaceous : Genus 

 Corydalis 45. Papaveraceae. 



3. Sepals or calyx lobes more than 2; corolla not or inconspicuously spurred, 



usually pealike (reduced to 1 petal in Amorpha) ; leaves variously 



compound 54. Leguminosae. 



2. Leaves simple, sometimes palmately lobed or parted (4). 



4. Carpels normally more than 1, separate, in fruit becoming several-seeded 



follicles; leaf blades palmately cleft to parted; flowers showy, normally 

 blue or bluish, very irregular, the sepals larger than the petals and 

 similarly colored: Genera Delphinium, Aconitum. 



42. Ranunculaceae. 



4. Carpel solitary or, if more than one, united to form -a single fruit (5). 



5. Stems mostly woody; leaf blades entire; petals purplish red; fruit spiny, 



turgid, indehiscent, and the leaf blades narrow, or fruit a flat, 



dehiscent pod, and the leaf blades round-cordate: Genera Krameria, 



Cercis 54. Leguminosae. 



5. Stems mostly herbaceous ; fruit not spiny ; leaf blades not round-cordate 

 and entire or, if so, then the corolla spurred, white, yellow, or violet 

 (6). 

 6. Leaf blades palmately cleft or parted; fruit a thick-walled capsule, 

 2 cm. long or longer; stamens many__ 80. Cochlospermaceae. 

 6. Leaf blades entire or with shallowly toothed margins; fruit thin- 

 walled, much less than 2 cm. long; stamens 12 or fewer (7). 

 7. Stipules present; sepals, petals, and stamens 5__ 82. Violaceae. 

 7. Stipules none or reduced to glands (8) . 



8. Filaments separate, borne on the calyx: Genus Cuphea. 



87. Lythraceae. 

 8. Filaments more or less united (9) . 



9. Petals 2; stamens 3; capsule turgid, 4-lobed. 



48. Resedaceae. 

 9. Petals commonly 3; stamens 6 to 8; capsule flat, 2-celled. 



63. Polygalaceae. 

 1. Corolla regular or nearly so (10). 



10. Ovary inferior, at least the lower part distinctly adnate to the hypanthium 

 or calyx tube (11). 

 1 1 . Petals and stamens indefinitely numerous ; stems very thick and succulent, 

 flat or cylindric; leaves none or greatly reduced and terete. 



85. Cactaceae. 



