112 American Midland Naturalist Monograph No. 7 



12. Inflorescence corymbose; endocarp of the ripe carpels 



hard and bony; branches usually with spines 



19. Crataegus 



8. Leaves pinnate; flowers in terminal compound cymes; petals 

 roundish; styles 3, free; anthers white; pome small, berry-like, 



red, acid, 3-loculed; branches not spiny 15. Sorbus 



2. Pistil 1, simple, superior, 2-ovuled; style 1; fruit a 1-seeded drupe; 



leaves simple 20. Prunus 



1. Herbs; pistils several to many, simple, superior; fruit achenes, drupelets, or 

 follicles. 

 14. Pistils 2-5, becoming 2- to 4-seeded follicles. 



15. Leaves trifoliolate or 3-parted, nearly sessile; stipules large; flowers 



white or pinkish, in loose terminal panicles 4. Gillenia 



15. Leaves pinnately compound. 



16. Leaves 2- to 3-pinnate; stipules minute or none; flowers numer- 

 ous, unisexual, in a large panicle; petals white, about 1 mm 



long; follicles reflexed, usually 2-seeded 3. Aruncus 



16. Leaves pinnately 3- to 9-lobed or -foliolate; flowers perfect, 



pink or purple, in dense cymose panicles 7. Filipendula 



14. Pistils one to many, becoming 1-seeded achenes or drupelets. 



17. Pistils ripening into pulpy drupelets, forming a red raspberry; style 

 terminal or nearly so; leaves 3-5-foliolate; petals white or pink 



11. Rubus 



17. Pistils ripening into achenes. 

 18. Calyx not bristly. 



19. Pistils several to many; petals present; calyx usually with 5 

 sepal-like bractlets alternating with the sepals. 

 20. Style deciduous from the mature achene. 



21. Receptacle becoming succulent, red (or white), and 

 edible in fruit (a strawberry); petals white (or 



pink), obtuse; leaves trifoliolate 5. Fragaria 



21. Plants not as above 6. Potentilla 



20. Style persistent on the achene, jointed or plumose 



8. Geum 



19. Pistils 1-3; sepals 4, petaloid; petals none; achene usually 

 solitary, enclosed in the 4-angled calyx-tube; flowers (in 



our species) white, in a dense cylindrical spike 



9. Sanguisorba 



18. Calyx-tube with hooked bristles; flowers yellow, in spike-like 



racemes; achenes 2 10. Agrimonia 



] . Physocarpus Maxim. — Ninebark 

 {Opulaster Medic; Physocarpa Raf. ) 

 P. opulifolius (L.) Maxim. River banks, local. May-June. [P. 

 intermedins (Rydb.) Schneid.]. 



2. Spiraea L. 

 1. Leaves glabrous or nearly so; follicles glabrous. 



2. Sepals acute; inflorescence glabrous or nearly so; rarely found 



as an escape from cult S. latijolia (Ait.) Borkh. 



2. Sepals obtuse; inflorescence puberulent; moist ground. July- 

 Aug. Meadowsweet S. alba DuRoi 



