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. Jackii Sarg. Rhodora 5: 162. 1903.
C. rotundata Sarg. Ont. Nat. Sci. Bull. 4: 61. 1908.
A round-topped shrub, sometimes 15° high. Spines numerous, 11/2'-2 1/2' long; leaves ovate-orbicular to obovate, acute at the apex, cuneate or rounded at the base, 1 1/4'-2 1/2' long, 1'-2' wide, doubly serrate, lobes very shallow, dull dark green above, slightly pubescent becoming glabrate above, paler and glabrous beneath; corymbs slightly villous; flowers 10"-12" broad; calyx glabrous, its lobes sharply glandular-serrate; stamens 5-10; anthers yellow; styles and nutlets 2 or 3; fruit ovoid-ellipsoid, 5"-8" thick, dull dark red, prominently angled; flesh thick, reddish, edible.
Isle of Montreal to southern Ontario. May; fruit ripe September.
Crataegus ovata Sarg. Man. Trees 402. 1905.
A tree, sometimes 300 high, with yellow, scaly, bark similar to that of a young Platanus, the spines 1' long. Leaves ovate-elliptic or obovate, 1 1/4'-2 3/4' long, 3/4'-2' wide, obtuse or acute at the apex, broadly cuneate or rounded at the base, coarsely serrate or doubly serrate, often with irregular crenate lobes towards the apex, dark green, shining and glabrous above, paler beneath, membranous; corymbs glabrous; flowers about 6" broad; stamens about 20; styles and nutlets usually 5; calyx-lobes lanceolate, entire; fruit globose or compressed-globose, yellow to orange-red, 3" or 4" thick, calyx-lobes appressed, usually deciduous.
River bottoms, western Kentucky and eastern Missouri. April-May; fruit ripe October.
Crataegus viridis L. Sp. Pl. 476. 1753.
C. arborescens Ell. Bot. S. C. & Ga. 1: 550. 1821.
A tree, often 35o high, with ascending branches and a broad crown, the bark gray or light orange. Spines rather uncommon, ¥-2' long; leaves oblong-ovate, acute, acuminate or even obtuse at the apex, serrate or doubly serrate, often with acute or obtuse lobes towards the apex, 3/4'-3 1/4' long, 1/2'-2' wide, dark green, shining and slightly impressed-veined above, sometimes pubescent along the veins beneath; corymbs glabrous; flowers 5"-8" broad; stamens about 20; anthers usually yellow, sometimes pink; styles and nutlets 4 or 5; fruit globose or compressed-globose, bright red or orange, glaucous, 2" or 3" thick.
Alluvial soil along streams and lakes, southern Virginia to northern Florida, Indiana, Illinois, Kansas and Texas. Wood hard, reddish-brown, weight per cubic foot 40 lbs. Red haw. Tree-haw or -thorn. March-April; fruit ripe October.