400 ROSACEAE 



salverform, or tubular. Sepals normally 5, rarely 4 or 6-9, often subtended 

 by as many bractlets. Petals as many as the sepals or rarely wanting. 

 Stamens 1-many, most commonly 20, in three series. Gynoecium of 1- 

 many usually wholly distinct carpels. Fruit of achenes, follicles, or drupe- 

 lets. 



A. Fruit consisting of 1-5 dehiscent follicles. 



Carpels alternate with the sepals, or less in number; stipules none or deciduous. 



Carpels 1-5, if more than one more or less united below; seeds shining, pear-shaped, 



with a bony coat; endosperm present. 1. OPULASTER. 



Carpels usually 5, distinct; seeds dull, linear or linear-lanceolate, with a thin coat; 



endosperm lacking. 

 Stamens inserted on the margin of the hypanthium; flowers perfect; shrubs or 



undershrubs with simple leaves. 

 Filaments free; leaves entire or toothed. 



Carpels dehiscent on the ventral suture: shrubs with deciduous leaves. 



2. SPIRAEA. 

 Carpels dehiscent on both sutures; cespitose tufted undershrubs with 



persistent leaves. 

 Flowers racemose, rarely somewhat paniculate; stamens 20. 



3. PETROPHYTUM. 

 Flowers solitary, nearly sessile at the ends of the short branches; 



stamens 10. 4. KELSEYA. 



Filaments united at the base; leaves twice or thrice 3-cleft. 



5. LUETKEA. 

 Stamens inserted on the inside of the hypanthium; flowers dioecious; tall herbs 



with twice or thrice compound leaves. 6. ARUNCUS. 



Carpels opposite to the sepals; stipules present, persistent; leaves pinnately dissected. 



7. CHAMAEBATIARIA. 

 B. Fruits consisting of indehiscent achenes or drupelets. 



I. Carpels not enclosed in a fleshy hypanthium. 

 a. Fruits of dry achenes. 



1. Ovules 2, one above the other; achenes usually 1 -seeded and more or less 

 flattened, arranged in a single circle; shrubs with simple leaves. 



8. SERICOTHECA. 



2. Ovules and seeds solitary; achenes usually turgid and, if many, spirally 



arranged. 



a. Seeds inserted at the distal end of the ovary, i. e., opposite the origin 

 of the style, pendulous or in genera with basal styles ascending; 

 radicle superior. 

 Disk at the mouth of the hypanthium annular or obsolete; leaves and 



branches alternate. 



Style articulated to the ovary; hypanthium from campanulate to 

 almost flat, neither contracted at the throat nor closely 

 investing the achenes; flowers cymose or solitary. 

 St^le not basal. 



Style terminal or nearly so; ovules pendulous and anatropous. 

 Stamens separated from the receptacle by an open space; 

 no indication of an annular thickening at the base 

 of the filaments. 



Hypanthium saucer-shaped to deeply campanulate; 

 petals oblanceolate to obcordate or cuneate; 

 pistils usually more than 2. 

 Filaments dilated, petaloid. 9. HORKELIA. 

 Filaments filiform. 10. IVESIA. 



Hypanthium wheel-shaped; petals narrowly linear; 



pistils 2. 11. COMARELLA. 



Stamens inserted very near the base of the receptacle on 

 a more or less evident annular thickening. 



12. POTENTILLA. 



Style lateral; ovules ascending and amphitropous. 

 Achenes glabrous; herbs. 



Achenes numerous; stamens about 20. 

 Leaves odd-pinnate. 



Receptacle not enlarged in fruit; petals yellow, 

 obtuse or retuse; leaves interruptedly pin- 

 nate. 13. ARGENTINA. 

 Receptacle somewhat enlarged in fruit, becom- 

 ing spongy; petals red, acute or acuminate; 

 leaves regularly pinnate. 



14. COMARUM. 



Leaves trifoliolate; receptacle much enlarged and 

 usually red in fruit, pulpy; petals white or 

 pinkish. 15. FRAGARIA. 



Achenes 10-15; stamens 5; leaves trifoliolate. 



16. SIBBALDIA. 



Achenes hairy; shrubs; style club-shaped; leaves pinnate; 

 petals (in ours) yellow. 17. DASIPHORA. 



