This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
C. monogyna Jacq. Fl. Aust. 3: 50. pl. 292. f. I. 1775.
A shrub or tree, with ascending branches, sometimes 400 high and a trunk diameter of 1 1/2°. Thorns numerous; leaves ovate, sharply 3-15-lobed or cleft, acute at the apex, cuneate to truncate at the base; serrate, 1/2'-1 3/4' long, \'-2.' wide, dark green and glabrous above when mature, paler and slightly pubescent beneath; corymbs many-flowered, glabrous; flowers white or pink, about 7" broad; calyx-lobes deltoid, entire, obtuse; stamens about 20; anthers pink; style and nutlet usually one; fruit globose or subglobose, red, about 3" thick.
Along roadsides and in thickets, sparingly escaped from cultivation. Wood hard, yellowish white; weight per cubic foot 50 lbs. Native of Europe and Asia. May-June; fruit ripe September. Has been confused with C. Oxyacantha L. Called also English hawthorn. Hathorn. Hedge-thorn. May-bush. May. Quickset. Quick. Wick. Wicken. Haw-tree. Quickthorn.
C. Marshallii Eggl. in Britton & Shafer, N. A. Trees 473.
A shrub or small tree, 7°-20° high, the stems usually crooked; branches spreading; bark smooth; twigs tomentose; spines few, 1'-1 1/2' long. Leaves broadly ovate to orbicular, acute, slightly cordate to cuneate at the base, pinnately 3-7-lobed, serrate, 1/2'-1 1/2' long and wide, pilose above when young, pilose beneath, membranous; petioles l'-2' long, tomentose; corymbs 3-12-flowered, usually villous; flowers 6"-8" broad; calyx-lobes lanceolate, acuminate, serrate, glabrous outside; stamens about 20; anthers dark red; styles and nutlets usually 2; fruit ellipsoid or ovoid, 2"-4" long, scarlet, slightly pubescent; calyx-lobes reflexed; nutlets smooth on back, bare at apex.
C. spathulata Michx. Fl. Bor. Am. 1: 288. 1803. C. microcarpa Lindl. Bot. Reg. 22: pl. 1846. 1836.
A shrub or small tree, 15°-25° high, the bark light brown, smooth, flaky. Twigs glabrous; spines sparse, l'-1 1/2'; leaves spatulate or oblanceolate, 1/2' - 1 1/2' long, 1/4'-3/4' wide, acute or rounded and sometimes 3-5-lobed, sharply cuneate into a winged petiole, crenate-serrate, dark green and slightly villous above when young, membranous; flowers about 5" broad, several or numerous in glabrous corymbs; calyx-lobes deltoid, entire; stamens about 20; anthers pink; styles and nutlets usually 5; fruit globose or subglobose, red, 2" or 3" thick, calyx-lobes reflexed; nutlets slightly ridged on back, the apex bare.
Thickets at lower altitudes, Virginia to Florida, Missouri and Texas. Wood hard, reddish-brown. Weight per cubic foot 45 lbs. Narrow-leaved thorn. May-June.