ROSACEAE. 199 



Stamens 20; carpels 

 numerous. 

 Leaves trifoliolate; 

 receptacle fleshy 



in fruit. 283. Fragaria, 210. 



Leaves pinnate; re- 

 ceptacle not 

 fleshy. 

 Flowers dark- 

 purple; recep- 

 tacle spongy. 284. Comarum, 2n. 

 Flowers yellow 

 or whitish; 

 receptacle 

 dry. 

 Plant stolon- 

 iferous; 

 flowers sol- 

 itary. 285. Argentina, 2n. 

 Plant not sto- 

 loniferous ; 

 flowers cy- 

 mose. 286. Drymocallis, 2U. 



262. PRUNUS. Plum. Cherry. 



Small trees or shrubs, many with edible fruits; leaves alternate, 

 simple, usually serrulate; flowers white or rose-colored, solitary 

 or fascicled in the axils or in terminal racemes or corymbs; calyx 

 5-lobed, free from the ovary; petals 5, on the calyx-tube; stamens 

 numerous; pistil 1 ; style 1 ; ovary 1 -celled, 2-ovuled; fruit a drupe; 

 seed 1, rarely 2; endosperm none. 



Flowers in corymbs. P. emarginata. 



Flowers in racemes. P. demissa. 



Prunus emarginata erecta (Presl) Piper n. comb. {Cerasus ereda Presl; 

 Prmius etnarginata villosa Sudw.) Wild Cherry. Small tree, 10-20 m. high; 

 branches and bark chestnut brown, with prominent lenticels; leaves narrow, 

 ovate, elliptical or obovate, obtuse or acute, cuneate at base, minutely serrate, 

 tomentose beneath, 3-8 cm. long, short-petioled; corymbs few-flowered, ap- 

 pearing with the leaves, the pedicels pubescent; flowers about 1 cm. broad; 

 fruit oblong, bright red, bitter; stone with a grooved ridge on one side. 



In open woods, common. The trees reach a maximum diameter of about 

 50 cm. and a height of 20 m. 



Prunus demissa (Nutt.) Dietr. Chokecherry. Shrub or small tree, 2-8 m. 

 high; leaves ovate or oblong-ovate, cuneate, rounded or cordate at the base, 

 sharply serrate, 5-10 cm. long, sometimes somewhat pubescent beneath; 

 petioles 1-2 cm. long, appearing after the leaves; calyx somewhat glandular; 

 petals nearly orbicular; fruit globose, dark purple, 5-6 mm. in diameter, not 

 edible; stone globose. 



In open prairies. First collected by Nuttall near the mouth of the Willa- 

 mette River. 



263. OSMARONIA. 



Shrubs with alternate simple entire leaves; stipules none; 

 flowers polygamo-dioecious, white, in loose nodding racemes, 



