=1.= Linnaeus _Sp. Pl._ 475. 1753. =2.= Hudson _Fl. Anglic._ 186. 1778. =3.= Ehrhart _Beitr. Nat._ =4=:16. 1789. =4.= Pursh _Fl. Am. Sept._ =1=:333. 1814. =5.= Hooker _Fl. Bor. Am._ =1=:167. 1833. =6.= Torrey and Gray _Fl. N. Am._ =1=:408. 1840. =7.= Koch, K. _Dend._ =1=:98. 1869. =8.= Ibid. _Deut. Obst._ 143. 1876. 9. DeCandolle _Or. Cult._ Pl. 212. 1885. 10. Schwarz _Forst. Bot._ 339. 1892. 11. Koch, W. _Syn. Deut. und Schw. Fl._ =1=:726. 1892. =12.= Dippel _Handb. Laubh._ =3=:637. 1893. =13.= Koehne _Deut. Dend._ 316. 1893. =14.= Beck von Managetta _Nied. Oester._ 818. 1893. =15.= Bailey _Cyc. Am. Hort._ 1447 fig. 1901. =16.= Schneider _Handb. Laubh._ =1=:628. 1906. Plant low, spreading, much-branched, thorny, shrubby, seldom attaining the dimensions of a small tree; branchlets distinctly pubescent; leaves small, ovate or oblong-ovate, sometimes obovate, numerous, nearly glabrous at maturity, obtuse at the apex, cuneate or rounded at the base, margins closely and finely serrate. Flowers white, one-third or one-half inch in diameter, expanding before the leaves; borne singly, in pairs or sometimes in threes, in lateral clusters. Fruit globose, usually less than one-half inch in diameter, dark blue, almost black, with a heavy bloom; flesh juicy, firm, with an acid, austere taste, scarcely edible for a dessert fruit but making a very good conserve; stone turgid or but little flattened, acute on one edge. European botanists commonly break the species into a number of sub-species, as:—_Prunus spinosa typica_ Schneider,[74] flower-pedicels and calyx-cup glabrous; _Prunus spinosa praecox_ Wim. and Grab.,[75] pedicels short, blossoms appearing before the leaves; _Prunus spinosa sessiliflora_ Beck,[76] with sessile flowers, possibly the same as the next preceding form; _Prunus spinosa coatanea_ Wim. and Grab.[77], blossoming with the leaves and with long pedicels; and _Prunus spinosa dasyphylla_ Schur.[78], flower-pedicel and calyx-cup more or less hairy. Besides these botanical sub-divisions there are several horticultural forms as follows: