44 ROSACEAE 



PRUNUS L. Plum CHERRY. Calyx 5-toothed. urn-shaped or campanulate, 

 falling away after flowering. Petals 5. Stamens 15-20. Pistil 1. Ovary 1, 

 with 3 pendulous ovules. Fruit a fleshy drupe, with a bony nucleus. 



* Flowers expanding before the leaves. 



P. americana Mars. Wild Plum. A shrub or small tree, 10-20 feet high, 

 thorny; leaves oblong, ovate or obovate, serrate, sometimes doubly serrate, 

 petioled, veiny; flowers in clusters, white, fragrant, fruit roundish, K inch or 

 more in diameter, yellowish or red, edible, skin tough. Flowers in April, 

 fruit ripe in August; rich woods; common throughout the state. 



* * Flowers cx})nndiny with the leaves. 



P. pennsylvanica L. f. WlhlRcd Cherry. A small tree, 15-30 feet high; 

 leaves oblong-lanceolate, pointed, finely and sharply serrate, glabrous, shin- 

 ing on both sides; flowers white, in lateral corymbose leafless clusters; drupe 

 globcse, small, red, flesh sour. Woods: April-June; rare; Fayette county, re- 

 ported from Story county. 



* * * Flowers terminating leafy branches, appearing after the leaves. 



P. serotina Ehrh. Wild Black Cherry. Tree 20-30 feet or more high, 

 branches reddish brown; leaves ovate-oblong or elliptical, taper pointed, ser- 

 rate, teeth glandular, incurved; petioles with 2-4 glands; flowers small, white, 

 in an elongated raceme; drupe small, black. Woods; May; common. 



P. virginiana L. Choke Cherry. Shrub 4-15 feet high, bark grayish; leaves 

 oval or obovate, short pointed, finely and sometimes doubly serrate, teeth 

 slender, petioles with two glands; flowers white, in a short raceme; drupe 

 small, red, turning dark. Woods; May; common; usually blooming a week 

 or more before the preceeding. 



AMYGDALUS L. Represented in cultivation by the Peach. 

 A. persica L. This species is a not infrequent escape in southern Iowa. 

 Waysides; April; Ringgold, Fayette, Page, and Fremont counties. 

 ROSACEAE B. Juss. Rose* Family. 

 Trees, shrubs, or herbs, with alternate mostly stipulate simple or com- 

 pound leaves, and regular perfect or polygamo-dicecious flowers. Calyx 

 usually 5-lobed, free or adnate to the ovary, often with a row of bractlets. 

 Petals usually 5, sometimes none. Stamens usually many, distinct, in- 

 serted with the petals on the edge of the disk which lines the calyx-tube. 

 Carpels 1-many. Ovary 1-celled or imperfectly 2-celled; style lateral or 

 terminal. Commonly includes the preceeding and the following families. 

 * Pistils usually 5, becoming 2-4-seeded follicles. 

 Spikaea. Leaves simple or pinnate ; flowers perfect or dioecious; pods 1-valved. 

 Physocahpus. Leaves palmately lobed ; flowers perfect ; pods 2-valved. 



* * Pistils few or many, 2-ovulcd, becoming I -seeded drupelets. 

 Rubus. Pistils many ; drupelets pulpy, crowded upon a spongy receptacle, 



* * * Pistils few or many, 1-ovulcd, becoming dry uchencs. 

 Geum. Leaves interruptedly pinnate; styles persistent, often hairy or plumose. 

 FRAGARIA. Leaves 3-foliate ; styles deciduous; receptacle enlarged and pulpy in fruit . 

 POTBNTILiLA. Leaves pinnately compound or digitate ; calyx with a row of bractlets alter- 

 nate with the calyx-lobes; stamens and achenes many; receptacle dry. 



* * * * Pistils 1-t, becoming achenes and enclosed in the dry persistent 



calyx-tube. 



AGBLMOHIA. Flowers yellow, in long racemes; calyx bearing hooked prickles. 



***** Pistils many, becoming bony advenes and enclosed in a fleshy 

 persistent pome-like calyx-tube. 



Rosa. Prickly shrubs or herbs ; the only genus. 



