166 ROSACE^E. Prunus. 



21. Acaena. Calyx-lobes valvate, deciduous ; the tube oblong, becoming armed with barbed 



prickles. Petals none. Perennial herbs, with pinnate leaves, and densely spicate-clus- 

 tered flowers. 



22. Poterium. Calyx-lobes imbricate, deciduous, petaloid ; the tube 4-angled, naked. Petals 



none. Herbs with pinnate leaves, and densely capitate or spicate flowers. 



TRIBE V. ROSE^E. Carpels many, in fruit bony akenes, enclosed and concealed in the 

 globose or urn-shaped fleshy calyx-tube, which resembles a pome. Petals conspicuous. 

 Stamens numerous. 



23. Rosa. The only genus. Erect shrubs, with pinnate leaves. 



SUBORDER III. POMKE. 



Carpels 2 to 5, enclosed in and mostly adnate to the fleshy calyx-tube, in fruit 

 becoming a 2 several-celled pome. Ovules erect or ascending, a pair in each carpel 

 (more numerous in cultivated apples), ascending. Styles often united below. 

 Trees or shrubs, with stipules free from the petiole or nearly so. 



* Evergreen : carpels partly free and separating. 



24. Heteromeles. Carpels only 2, tomentose above, lightly united and in flower nearly supe- 



rior, becoming thin and papery, and closely included in the beny-like calyx. 



* * Deciduous-leaved : carpels 2 to 5, united and coalescent with the fleshy or berry-like calyx. 



25. Crateegus. Ovary 2 - 5-celled ; the fruit drupaceous, of 2 to 5 bony 1 -seeded stones, either 



separable or united into one. Branches usually thorny. 



26. Pyrus. Ovary 2 - 5-celled ; the fruit a proper pome, with papery or cartilaginous and undi- 



vided 2-seeded cells or carpels. 



27. Amelanchier. Ovary 5-celled ; the cells 2-ovuled and 2-seeded, but in fruit each divided 



into two by a partition from the back. Otherwise like Pyrus. 



ANOMALOUS GENUS. 



28. Canotia. Calyx free from the septicidally 5-valved exserted capsule. Cells 1-seeded. Sta- 



mens 5, hypogynous. A leafless shrub, with solitary flowers. 



1. PRUNUS, Tourn. PLUM, CHERRY, &c. 



Calyx campanulate or turbinate, 5-cleft, deciduous. Petals 5, spreading. Stamens 

 15 to 25, inserted with the petals. Ovary solitary, free, with 2 pendulous ovules : 

 style terminal. Fruit a more or less fleshy drupe, with usually a bony stone con- 

 taining one or rarely two seeds. Trees or shrubs ; leaves alternate, simple, usually 

 serrulate; flowers white or rose-colored, solitary or fascicled in the axils, or in 

 terminal racemes. 



Species about 80, widely dispersed through the northern hemisphere, but mostly confined to 

 temperate regions. Of the 20 North American species, 14 are found only in the Atlantic States, 

 from Canada to Mexico. This comprehensive genus now includes several of our most delicious 

 and useful fruits, formerly referred to several genera, such as the Almond, with a somewhat 

 fibrous pitted stone, P. (Amygdalus) communis, the Peach and Nectarine, with wrinkled stone, 

 P. (Amyydalus) Persica, the Apricot, P. Armeniaca (Armeniaca vulgaris), the Garden Plum, 

 P. domestica, the Sloe, P. spinosa, the Garden Cherries, P. Cerasus (Ccrcisus vulgaris}, also 

 the Cherry-Laurel, P. Lauro-Cernsus (Laurocerasus officinnlis), &c. Many of the species have 

 medicinal virtues, and the principle or elements of prussic (cyanohydric) acid so abound in some 

 species, especially in their kernels and bark, as to make them actually poisonous when eaten 

 freely. The foliage and young branches of some of the Cherries become poisonous to cattle when 

 wilted. The six Californian species represent nearly as many sections, which have been more or 

 less recently regarded as genera, but the limiting characters prove to be too indefinite. The 

 American species of Plum (belonging to the first section) differ from those of the Old World in 

 having the leaves folded (conduplicate) instead of convolute in the bud, the fruit with little or 

 no bloom, and some of them have very turgid instead of flattened stones, thus connecting this 

 section with the following one. 



