FLOWERING PLANTS AND FERNS OF ARIZONA 47 



18. Ovary superior; plants aquatic or semiaquatic; leaves 

 not equitant 15. Poxtederiaceae. 



18. Ovary inferior; plants terrestrial; leaves equitant (in 2 

 ranks, enfolding one another) 19. Iridaceae. 



AXGIOSPERMAE-DICOTYLEDOXEAE 



Series 1. Apetalae 



Key to the families 



1. Rowers (of one or both sexes* in catkins or catkinlike racemes or spikes; 

 plants mostly trees or shrubs (2). 

 2. Pistillate flowers solitary or in few-flowered clusters, the staminate flowers 

 in catkins - 3 . 

 3. Fruit small, achenelike, enveloped by a winged calyx; leaves narrow, 



entire, fleshy: Genus Sarcobatus 34. Chexopodiaceae. 



3. Fruit large, nutlike; leaves large, not fleshy (4 . 



4. Leaves pinnately compound; nut with a thick hard shell; cotyledons 



2-lobed 23. Juglaxdaceae. 



4. Leaves simple 'sometimes deeply lobedi; nut (acorn) with a relatively 

 thin shell, partly enclosed in a cuplike involucre; cotyledons entire. 



25. Fagaceae. 

 2. Pistillate and usually the staminate flowers in catkins or catkinlike in- 

 florescences (5). 

 5. Flowers monoecious, the pistillate ones subtended by conspicuous bracts; 



mature catkins dry 24. Bettlaceae. 



5. Flowers dioecious or, if monoecious, not conspicuously bracted and the 

 pistillate catkins fleshy at maturity (6). 

 6. Perianth none; fruit a capsule; seeds with a conspicuous tuft of silky 



hairs 22. Salicaceae. 



6. Perianth present, at least in the staminate flowers I 7 . 



7. Fruits numerous, fused into a compound fleshy fruit, or dry and 

 subtended by conspicuous papery bracts; leaf blades usually 



lobed, thin 27. Moraceae. 



7. Fruits, remaining separate; leaf blades entire, thick: Genus Garrya. 



92. Corxaceae. 

 1. Flowers not in catkins N . 



8. Ovary inferior or appearing so, wholly or partly adnate to the perianth 

 tube or in fruit very closely enveloped by it - 9 . 

 9. Plants aquatic (the stems wholly or partly immersed in water ; leaves 

 entire and in whorls, or the immersed ones filiform-dissected; flowers 



minute, axillary 89. Haloragidaceae. 



9. Plants not aquatic 1 10 . 



10. Perianth really double but appearing single and corollalike; calyx 

 with tube wholly adnate to the ovary and the limb obsolete or 

 reduced to a mere border: Families properly of the series Polypetalae 

 and Gamopetalae (11). 

 11. Fruit a pair of contiguous, 1 -seeded carpels '12). 



12. Flowers in umbels; leaves alternate or basal, mostly compound. 



91. Umbelliferae. 



12. Flowers in cymes or solitary in the axils; leaves appearing ver- 



ticillate, simple: Genus Galium 116. Rubiaceae. 



11. Fruit achenelike, not paired (13). 



13. Flowers in heads subtended by an involucre: corolla tubular, 



funnelform, or strap-shaped, not spurred: anthers often connate. 



121. Compositae. 



13. Flowers not in involucrate heads but sometimes in rather dense 



clusters: corolla spurred: anthers not connate: Genus Plectritis. 



118. Yaleriaxaceae. 

 10. Perianth evidently in one series, calyxlike or corollalike (14). 

 14. Plants parasitic on the steins of trees and shrubs (15). 



15. Stems well developed, much branched: leaves with well-developed 

 blades, or reduced to small scales: fruit a 1-seeded berry. 



29. LORAXTHACEAE. 



286744" 





