64f.16. Crataegus Linnaeus (sect. Coccineae) ser. Parvifoliae (Loudon) Rehder, Man. Cult. Trees ed. 2. 366. 1940.
Crataegus sect. Parvifoliae Loudon, Arbor. Frutic. Brit. 2: 841. 1838
Shrubs, 10–50 dm, ˂± xeromorphic˃, multi-stemmed. Stems: trunk bark gray-brown, rough; ˂branches spreading; twigs ± straight˃, new growth pubescent, 1-year old gray-brown or brown, older gray; thorns on twigs usually numerous, sometimes absent, straight, rarely slightly recurved, 1-year old blackish, fine, 3–5(–8) cm. Leaves: petiole nearly absent, sessile-glandular or eglandular; blade ˂dark green˃, elliptic to narrowly obovate or similar, sometimes suborbiculate, (1–)2–3.5(–6) cm (small, usually longer than wide), coriaceous, base ± cuneate, lobes 0, or 1(or 2) per side, sinuses shallow, lobe apex obtuse, margins crenate or crenate-serrate, ˂teeth often gland-tipped, glands black˃, venation ± craspedodromous to semicamptodromous, veins 3 or 4(or 5) per side, apex broadly acute to rounded, surfaces pubescent. Inflorescences 1–3(–6)-flowered, reduced corymbs; branches moderately to densely pubescent; bracteoles of two types: 1) not occurring in all specimens, ± persistent, green, narrowly elliptic, herbaceous, margins strikingly toothed, glandular, or 2) occurring in all specimens, ± caducous, linear, small, membranous to herbaceous, margins stipitate-glandular. Flowers 10–18 mm diam.; hypanthium densely tomentose; sepals narrowly triangular, equal to or longer than petals, margins usually glandular-serrate, often deeply so (except in C. uniflora); stamens 20, anthers white to cream or ivory; styles (3–)5. Pomes yellowish or red to ruddy, sometimes dull brown, suborbicular, 8–12(–14) mm diam., pubescent to tomentose; flesh mealy or not recorded; sepals patent or reflexed, ˂glandular-serrate, often deeply so, non-accrescent˃; pyrenes (3 or)4 or 5.
Species 2 (2 in the flora): se United States, ne Mexico.
Series Parvifoliae contains two species: Crataegus uniflora, widespread and often common in the coastal plain from Texas to Long Island, New York, more sparse inland to Missouri and Illinois and in Tamaulipas, Mexico; and C. brittonii, much rarer, from North Carolina and adjacent states. Crataegus choriophylla Sargent may not belong in this series; it is a rare, perhaps extinct, tree with distinctly petiolate, thin, strongly toothed, often slightly incised leaves, 3–5-flowered inflorescences, cream anthers, and orange-red pomes. Crataegus ×vailiae, a putative interserial hybrid with ser. Macracanthae, keys out in the second couplet because of its long foliaceous sepals.
Features that best characterize ser. Parvifoliae are relatively small stature, rather glandular plants, relatively small, more or less unlobed leaves, uniflorous to few-flowered inflorescences, relatively small flowers, more or less foliaceous sepals equal to or longer than the petals, and ivory to cream anthers.
Members of ser. Parvifoliae share characteristics with members of ser. Triflorae, but their plant parts are so much smaller that even casual confusion is not possible. At least in some specimens, the series shares the characteristic with Triflorae that some flowering shoots are leafy shoots of the season borne directly on the extension shoots and not subterminally on woody short shoots. Confusion is quite frequent with smaller members of ser. Lacrimatae. Members of both series contain small- to medium-sized xeromorphs that are rather glandular, often hairy, and often have yellowish pomes. Members of ser. Lacrimatae, though, may be readily distinguished by their strongly flexuous twigs, entire or glandular-serrate sepals much shorter than petals, and fewer styles and pyrenes.
SELECTED REFERENCE Phipps, J. B. and K. A. Dvorsky. 2006. Crataegus ser. Parvifoliae and its putative hybrids in the southeastern United States. Sida 22: 423–445.