158 CASSIACEAE. 



4. P. Cerasus L. Small tree: leaf -blades ovate, oval-ovate, or ovate-lanceolate, 

 4-11 cm. long, abruptly acute or acuminate, finely serrate-dentate, glabrous, 

 resinous when young: corolla 1.5-2.5 cm. broad: drupes nearly globose, 8-10 

 mm. in diameter, or larger in cultivation, sour, red or black: stone subglobose. 



— Eather common, in fence-rows and woods. Nat. of Eu. — Sour-cherry. 



MORELLO-CHERRY. 



5. p. Avium L. Large tree: leaf -blades ovate to oval or oval-ovate, 5-10 cm. 

 long, abruptly short-acuminate, coarsely doubly serrate, pubescent beneath, 

 sometimes only on the veins: corolla 2.5-3 cm. broad: drupes ovoid-globose, 

 8-10 mm. in diameter, not acid, usually sweet : stone globular. — Common, in 

 woods, fence-rows, and thickets. Nat. of Eu. — Sweet-cherry. Mazzard. 



6. P. americana Marsh. Small somewhat spiny tree: leaf -blades elliptic to 

 oval or oval-obovate, 4-10 cm. long, acuminate, sharply singly or doubly ser- 

 rate, pubescent beneath, especially near the veins, acute or rounded at the 

 slightly inequilateral base: petioles usually glandless: flowers 2-5 in lateral 

 clusters: sepals entire: petals 7-10 mm. long: drupes subglobose or barely 

 elongate, 18^25 mm. long, sometimes with slight bloom: stone ovoid or oval, 

 flattened. — Common, in thickets and fence-rows. — Wild yellow- plum. Wild 



RED-PLUM. 



3. PADUS Borckh. Shrubs or trees. Leaves deciduous, manifestly im- 

 pregnated with prussie acid. Flowers in terminal racemes. Hypanthium green. 

 Sepals relatively large. Petals rounded. Drupe with a juicy exocarp. — Spr. 



— Wild cherry. 



Sepals deciduous : leaf -blades sharply serrulate. 1. P- nana. 



Sepals persistent : leaf-blades crenate-serrulate. 2. P. virginiana. 



1. P. nana (Du Eoi) Eoem. Shrub with diffuse branches, or small tree 

 with spreading or drooping branches and very bitter bark: leaf -blades thin- 

 nish, oval or obovate, 5-10 cm. long, sharply serrulate, usually rounded at the 

 base, glabrous or nearly so on both sides: racemes rather lax, 8-15 cm. long: 

 sepals reflexed, often ovate, glandular-margined: petals 3-4 mm. long: drupes 

 globose, 8-10 mm. in diameter, red or almost black, or rarely yellow, very 

 astringent. [P. virginiana Eoem, not Prunus virginiana L.] — S. Rare, in rocky 

 woods near the Octoraro Creek. — Schists. — Choke-cherry. 



2. P. virginiana (L.) Mill. Tree with ascending branches, becoming 35 m. 

 tall, the bark aromatic and bitter: leaf -blades firm, oblong or elliptic, varying 

 to obovate, or lanceolate, 5-15 cm. long, acuminate or acute at both ends, 

 or rounded at the base, crenate-serrulate with callous-tipped teeth, glabrous 

 or nearly so: sepals ovate, longer than broad: corolla 8-10 mm. broad: drupes 

 globose, 8-10 mm. in diameter, dark-purple or nearly black, sweet but slightly 

 astringent. [P. serotina (Ehrh.) Agardh.] — Common, in thickets and woods. 



— Wild black-cherry. Eum-cherry. 



Family 12. CASSIACEAE. Senna Family. 



Trees, shrubs, or herbs. Leaves alternate : blades compound, usually 

 1-2-pinnate, rarely 1-foliolate. Flowers perfect, polygamous, monoecious, 

 or dioecious, more or less irregular. Calyx of 3-5, usually slightly united, 

 sepals, sometimes borne on the edge of a well-developed hypanthium. 

 Corolla of 3-5 unequal distinct petals. Androecium of 6-10 distinct or 

 nearly distinct stamens. Gynoecium 1-earpellary. Fniit a legume. 



Corolla apparently papillionaceous : leaves with 1-foliolate blades. 1. Ceecis. 



Corolla more or less irregular, sometimes nearly regular : leaves 

 with pinnately compound blades. 



