Shrubs or trees, 20–50 dm. Stems: trunk bark dark, rough; twigs ± straight, new growth deep reddish green, glabrous or pubescent at first, 1-year old shiny, dark redbrown or glossy, brown to deep purple-brown, 2-years old dark reddish and gray, mid brown, or gray; thorns on twigs usually numerous, ± straight to recurved, 1-year old shiny, dark redbrown, deep brown, or black, slender to stout, 1.5–4 (–5) cm. Leaves deciduous; petiole length 25–40% blade, slender, eglandular or minutely sessile-glandular, glands black, sometimes stipitate-glandular distally, adaxial sulcus pubescent; blade broadly elliptic to elliptic-oblong, or elliptic-rhombic, 3.5–8 cm, length/width = 1.2–1.5, ± coriaceous to thin, base narrowly cuneate to cuneate-rounded, lobes 2–4 per side, sinuses moderately deep, max LII (0–) 15–25%, lobe apex subacute to acute, margins crenate-serrate or serrate, venation craspedodromous, veins (3–) 5–8 per side, absent to sinuses, apex acute to subacute, matte, abaxial surface glabrous, veins glabrous or scabrous, adaxial ± densely scabrous, sometimes glabrescent. Inflorescences 4–15-flowered; branches glabrous or densely pubescent to tomentose; bracteoles caducous, linear, membranous, margins sessile-glandular. Flowers 13–21 mm diam.; hypanthium glabrous or tomentose; sepals triangular to broadly triangular, 3–4 mm, margins usually finely glandular-denticulate; petals pale cream in C. rivuloadamensis, post-mature petals pale-brown; stamens 10, anthers pale-pink to pink; styles 3–5. Pomes ripening from bright to deep red, deep red to purple (often nearly black) or pale reddish purple, turning through deep red to reddish plum and burgundy, suborbicular to ellipsoid or turbinate, 8–12 mm diam.; sepals sessile, prominent, ± patent to recurved or subappressed; pyrenes 3–5, sides plane to slightly concave.

Distribution

sw Canada

Discussion

Species 3 (3 in the flora).

Series Montaninsulae is restricted to the Cypress Hills and is erected to accommodate a suite of species with predominantly purple fully ripe fruit and plane-sided pyrenes. The series shares characteristics with sect. Coccineae and sect. Douglasia and, pending further study, remains unassigned to a section. It is plausible that ser. Montaninsulae represents three different hybrid derivatives between the two sections; each of the species has distinctive characteristics and can be found repeatedly over county-sized areas in suitable habitats in the Cypress Hills. The two most similar species, C. rivulopugnensis and C. purpurella, differ primarily in fruit color, leaf shape, size, and venation, the former being the red-fruited member of the group; C. rivuloadamensis, much hairier, with the largest fruit and often short, stout, more or less conic thorns, is the most distinct species.

Selected References

None.

Lower Taxa

Crataegus purpurella, Crataegus rivuloadamensis, Crataegus rivulopugnensis

Key

1	Leaf blades 4–8 cm mature; inflorescence branches ± densely tomentose; flowers 17–21 mm diam., hypanthia densely pubescent except sometimes distally; pomes usually ± densely hairy.	Crataegus rivuloadamensis
1	Leaf blades 5–6 cm mature; inflorescence branches glabrate or ± pilose; flowers 13–16 mm diam., hypanthia glabrous or ± pilose, sometimes proximally only; pomes glabrous or sparsely pubescent	> 2
2	Twigs: thorns 2–3.5 cm; leaf blades broadly rhombic to broadly elliptic or oblong, 3.5–4.5(–5) cm mature, veins 3 or 4(or 5) per side, barely impressed; inflorescence branches glabrate to sparsely pilose; pomes deep red to red-burgundy younger, deep purple fully ripe.	Crataegus purpurella
2	Twigs: thorns 2.5–4(–5) cm; leaf blades broadly elliptic to ovate, 4–6 cm mature, veins 5–8 per side, slightly impressed; inflorescence branches ± pilose; pomes red, becoming bright to deep red.	Crataegus rivulopugnensis

"thin" is not a number."slender" is not a number.