FLOWERING PLANTS AND FERNS OF ARIZONA 389 



3. Leaves simple (4). 



4. Plants unarmed; ovary with complete and false partitions, the cells 

 twice as many as the number of styles; flowers relatively large, 

 in racemes or corymbose fascicles 7. Amelaxc hier. 



4. Plants armed with strong spines; ovary without false partitions, the 



^ cells of the same number as the styles; flowers relatively small, 

 in corymblike cymes 8. Crataegus. 



2. Ovary superior; calyx tube not fleshy and enclosing the pistils or, if so, 

 then not adnate to them (5). 



^5. Calyx tube (hypanthium) enclosing the numerous carpels, becoming 

 fleshy; fruit simulating a pome, crowned bv the persistent calyx 

 lobes 21. Rosa. 



5. Calyx tube not enclosing the carpels, or not becoming fleshy (6). 

 6. Fruits becoming juicy and more or less edible (7). 



7. Plants shrubby, often with prickly stems; receptacle not becoming 

 greatly enlarged and fleshy, bearing a conic, ovoid, or nearly 

 globose mass of more or less juicy drupelets 9. Rubus. 



7. Plants herbaceous, unarmed, acaulescent; receptacle becoming 



greatly enlarged and very fleshy, the numerous dry achenes 



embedded in its surface 10. Fragaria. 



6. Fruits not becoming juicy (8). 



8. Carpels becoming dehiscent capsules or follicles, containing usually 



more than one seed (9) . 

 9. Seeds with a thin, elongate, terminal wing; leaves evergreen, 

 simple; plant a large shrub or small tree. _ 4. Yauquelixia. 

 9. Seeds not winged; leaves not evergreen or, if si, then compound 

 (10). 

 10. Leaves more or less evergreen, bipinnate; stipules persistent; 

 herbage scurfy with stellate hairs and somewhat viscid. 



3. Chamaebatiaria. 

 10. Leaves deciduous, simple; stipules deciduous or none; herbage 

 not scurfy or viscid (11). 

 11. Plant a shrub; leaf blades large, rounded-cordate, usually 

 shallowly 3-lobed; flowers in corymbs; fruits much- 

 inflated 1. Physocarpus. 



11. Plant an undershrub; leaf blades small, spatulate, entire; 

 flowers in dense spikelike inflorescences; fruits not 



inflated 2. Spiraea. 



\ Carpels becoming indehiscent 1-seeded achenes, or sometimes 

 tardily dehiscent in Holodiscus (12). 

 12. Plants herbaceous above ground, the caudex often somewhat 

 woody; leaves pinnately or digitately compound (13). 

 13. Calyx tube 4-winged; bracts and margins cf the calyx lobes 

 scarious; petals none; flowers in dense cylindric spikes. 



20. Saxguisorba. 

 13. Calyx tube not winged; bracts and calyx lobes herbaceous; 

 petals present, sometimes minute; flowers not in dense 

 spikes (14). 

 14. Hypanthium bearing numerous hooked bristles; stems tall; 

 leaves pinnate, with several much smaller leaflets inter- 

 spersed among the large ones; flowers in slender, elon- 

 gate, spikelike racemes; petals yellow; pistils 2. 



19. Agrimoxia. 

 14. Hypanthium not bristly (15). 



15. Style (at least the lower portion) persistent on the achene 



often plumose 13. Geum. 



15. Style wholly deciduous from the mature achene (16). 

 16. Hypanthium with small bractlets, these alternate with 

 the sepals and simulating an outer series of calyx 

 lobes; pistils borne on a sessile receptacle, this flat, 



hemispheric, or low-conic __ 11. Potextit.la. 



16. Hypanthium without bractlets; pistils borne on a 

 stalked, cylindric or conic receptacle. 



12. Pubpusia. 

 12. Plants shrubby (17). 



17. Flowers in panicles, very numerous, very small; leaves sim- 

 ple, deeply cleft or coarsely toothed 5. Holodiscus. 



