128 ROSACEAE (ROSE FAMILY) 



a. Petals dark purple; receptacle spongy. W. E. — (Gk. komaros = 

 the Arbutus, from the resemblance of the fruits.) 



Comarum palustre (purple marsh-iocks) 



aa. Petals yellow or white; receptacle dry. 



b. Leaflets opposite; style attached near the base of the ovary ; flowers 



in cymes; plant without stolons. DRYMOCALLIS (p. 130) 



bb. Leaflets not opposite; style attached near the middle of the ovary; 



flowers solitary; plant with stolons. ARGENTINA (p. I2g) 



PHYSOCARPUS (Ninebark) 



Bark shreddy. Leaves alternate. Calyx segments s, persistent, stel- 

 late-hairy at least inside. Petals white or rarely pinkish. Stamens 20-40. 

 Pistils 1-5 ; styles terminal. Follicles somewhat united at base. Seeds 2-4. 

 — (Gk. physa = a bellows, carpos = fruit; from the inflated follicles.) 



A. Carpels usually 5, 8-10 mm. long; shrub 7 m, or less high. W. C. E. 



P. capltatus (tall ninebaek) 

 AA. Carpels usually 1-2, 3-5 mm. long; shrub 2 m. or less high. 

 B. Inflorescence bracts lanceolate; follicles inflated. E. P. monogynus 



BB. Inflorescence bracts spatulate or cuneate; follicles laterally flat. E. 



P. malvaceus 



SPIRAEA (Spiraea) 



Leaves evergreen or deciduous ; stipules none. Flowers perfect, in racemes 

 or corymbs or panicles. Calyx segments 5. Petals white or red. Stamens 

 15-70. Pistils 3-8, usually 5, distinct; styles terminal. Seeds 4. — 

 (Gk. speiran = to twist ; some species have twisted follicles.) 



A. Flowers red. 



B. Inflorescence flat-topped. W. C. E. S. denslflora (flat red spiraea) 



BB. Inflorescence not flat-topped. 

 C. Under side of leaves glabrous. 

 D. Twigs villous-puberulent. W. C. E. S. menziesii 



DD. Twigs glabrous. E. S. roseata 



CC. Under side of leaves tomentose. W. S. douglasU (haedhack) 



AA. Flowers white. 

 E. Inflorescence flat-topped. W. C. E. S. corymbosa (flat white spiraea) 



EE. Inflorescence not flat-topped. 

 F. Lower leaf surface tomentose. C. S. tomentulosa 



FF. Lower leaf surface not tomentose. C. E. S. pyramldata (pyramid bush) 



PETROPHYTUM 



Low, on rocks. Leaves oblanceolate or spatulate, coriaceous, evergreen. 

 FJowers in racemes ; racemes rarely compound. Calj^ segments 5. Petals 

 white. Stamens about 20. Pistils 3-5 ; ovary and lower part of style 

 very hairy ; style terminal. Seeds 2-4. — (Gk. pelros = a stone, phyton = 

 a plant ; referring to their rock habitat.) 



A. Leaves 3-veined. 

 B. Sepals obtuse: petals obovate or oval; leaves glabrous or nearly so. W. 



P. hendersoni 



