64f.12. Crataegus Linnaeus (sect. Coccineae) ser. Dilatatae (Sargent) Rehder, Man. Cult. Trees ed. 2. 362. 1940.
Crataegus [unranked] Dilatatae Sargent, Silva 13: 33. 1902
Shrubs or trees, 40–70 dm, main trunk dominant. Stems: trunk bark buff to darker, fibrous, checked into longitudinal plates, freshly exposed bark orange-brown; ˂branches spreading; twigs ± straight˃, new growth glabrous or pilose, 1-year old shiny, dark brown to sometimes tan, 2-years old deep gray, older pale; thorns on twigs numerous, usually ± recurved, 2-years old blackish, shiny, moderately thick, 3–6 cm. Leaves: petiole length 30–50% blade, glabrous or sparsely hairy, usually sparsely glandular, sometimes eglandular; blade ˂mid to dark green˃, ovate to broadly ovate or ovate-deltate, (4–)5–9(–11) cm, subcoriaceous, base subcordate to truncate or broadly cuneate, lobes 3–5 per side, sinuses shallow, lobe apex acute, margins ± serrate, ˂teeth large˃, venation craspedodromous, veins 5–7 per side, apex acute, abaxial surface glabrous, adaxial sometimes appressed-pubescent young. Inflorescences 5–12-flowered, convex panicles; branches glabrous or pilose; bracteoles caducous (larger ± persistent), ˂hyaline to red-tinged˃, (larger) oblong to curved, membranous to semiherbaceous, margins stipitate-glandular. Flowers 20–25 mm diam.; hypanthium glabrous or pilose; sepals triangular, much shorter than petals, margins glandular-laciniate; stamens 20; anthers white to rose-red; styles (4 or)5. Pomes bright pink to crimson, suborbicular, 10–20(–25) mm diam., glabrous or pubescent at ends; flesh ± hard (until overripe); sepals spreading or ± reflexed, ˂non-accrescent˃; pyrenes 5.
Species 1: c, e North America.
Series Dilatatae appears to be closely related to ser. Pruinosae, from which it is distinguished by often hairy adaxial leaf surfaces and inflorescence branches, at least some bracteoles more or less hard and persistent, more deeply dissected sepals, usually larger, non-angular pomes lacking elevated calyces, and by all the parts being equal to or greater than the normal upper size range for ser. Pruinosae.