FLOWERING PLAXTS AND FERXS OF ARIZONA 49 



21. Styles and (or) stigmas 2ormore, exceptionally 1 in family Euphorbiaceae 

 (32). 

 32. Stems woodv, the plants shrubs or trees (33). 

 33. Fruit a drupe (34). 



34. Style none; stigmas 2, elongate, spreading or recurved, plumose 

 or tomentose; ovary 1-celled; drupe with 1 stone; leaf blades 

 very unequal at base and very scabrous above. 



26. Ulmaceae. 



34. Style present (often very short) ; stigmas not recurved or 



plumose; ovary 2- or 3-celled; drupe with 1 to 3 stones; 

 leaf blades not conspicuously unequal at base or scabrous: 



Genera Condalia, Rhamnus 71. Rhamnaceae. 



33. Fruit not a drupe (35). 



35. Leaves palmately lobed or divided, or pinnate with few leaflets; 



fruit a pair of samaras, united at base, each with a 1-sided 



wing 69. Aceraceae. 



35. Leaves simple (palmately lobed in certain of the family Euphor- 

 biaceae) ; fruit not a pair of samaras (36) . 

 36. Fruit acornlike with 1 large seed; leaves entire, coriaceous. 



66. Buxaceae. 

 36. Fruit not acornlike (37). 



37. Ovary 2- to 4-celled (exceptionally 1-celled in the family 

 Euphorbiaceae) ; fruit a capsule, commonly longitudi- 

 nally dehiscent; flowers unisexual, in Dodonaea by 

 abortion (38). 

 38. Capsule not winged; leaves not viscid, entire to palmately 

 parted 64. Euphorbiaceae. 



38. Capsule conspicuously 2- to 4-winged; leaves somewhat 



viscid, narrow, entire: Genus Dodonaea. 



70. Sapixdaceae. 

 37. Ovary 1-celled: fruit not longitudinally dehiscent (39). 



39. Flowers perfect, subtended by a cylindric, turbinate, or 



cup-shaped, gamophyllous involucre; stamens 9; 

 fruit a 3-angled or winged achene: Genus Eriogonum. 



33. POLYGOXACEAE. 



39. Flowers perfect or unisexual, not with an involucre as in 

 the foregoing, but the pistillate flowers often sub- 

 tended by a pair of accrescent bractlets ; stamens 5 

 or fewer; fruit a utricle.-- 34. Chexopodiaceae. 

 32. Stems herbaceous or nearly so (40). 



40. Inflorescence of many small naked flowers in a dense cylindric 

 spike subtended by a conspicuous involucre of white petallike 

 bracts, the whole appearing like a single large flower. 



21. Saururaceae. 

 40. Inflorescence not as in the foregoing (41). 



41. Plants aquatic; stems wholly or partly immersed; stipules none; 

 fruit at maturity separating into 4 nutlets. 



65. Callitrichaceae. 

 41. Plants not aquatic or, if so, then the stems jointed and the 

 stipules united into a sheath around the stem (42) . 

 42. Ovary completely or incompletely 2- or more-celled, ex- 

 ceptionally 1-celled in the family Euphorbiaceae (43). 

 43. Fruit a depressed-globose, several-seeded berry ; plant a 

 coarse herb with large leaves: Genus Phytolacca. 



37. Phytolaccaceae. 

 43. Fruit a capsule (44) . 



44. Flowers unisexual, with or without a perianth. 



64. Euphorbiaceae. 



44. Flowers perfect, with a perianth 38. Aizoaceae. 



42. Ovary 1-celled (45). 



45. Fruit a many-seeded, longitudinally dehiscent capsule: 

 Genus Sagina 40. Caryophyllackae. 



