Rubus ser. Pallidi, W.C.R.Watson, 1946

Havlíček, Petr, Trávníček, Bohumil & Velebil, Jiří, 2022, Rubus violaceifrons (Rosaceae), a new bramble species from Bohemia (Central Europe, Czech Republic), Phytotaxa 568 (3), pp. 241-254 : 251

Determination key for identifying members of the Rubus ser. Pallidi occurring in the Czech Republic

1a Primocane stems glabrous (exceptionally with solitary hairs)............................................................................ R. holzfussii Sprib.

1b Primocane stems sparsely to densely hairy ...................................................................................................................................... 2

2a Prickles on primocane stems strongly declining, usually only 2.5–3 mm long; hairs 2–10(–25) on 1 cm length of primocane stem side; primocane leaves 3(–5)-foliolate. .................................................................................................................... R. scaber Weihe

2b Prickles on primocane stems patent to (usually slightly) declining, usually longer; hairs more than 20 (to very numerous) on 1 cm length of primocane stem side; primocane leaves (3–)5–foliolate ................................................................................................... 3

3a Terminal leaflet of primocane leaves most often elongated, with almost parallel sides, with distinctly cordate base of its lamina (also lateral leaflets usually with cordate base), with acuminate apex 20–25(–30) mm long, usually periodically (double) serrate, with relatively short petiolule (as long as 20–30% of its lamina length); primocane stems distinctly whitish glaucous (pruinous).. ....................................................................................................................................................................... R. posnaniensis Sprib.

3b Combination of shapes of primocane leaves different; primocane stems not distinctly whitish glaucous, on sunny side often suffused with dark violet-brown (vinaceous) ................................................................................................................................... 4

4a Terminal leaflet of primocane leaves very often distinctly convex; tip of inflorescence (infructescence) slightly nodding. – ........ ...................................................................................................................................................... R. siemianicensis (Sprib.) Sprib.

4b Terminal leaflet of primocane leaves flat; inflorescence (young infructescence) straight ............................................................... 5

5a Primocane stems with less than 15(–20) stalked glands on 1 cm length of stem side, densely hairy (usually with more than 50 hairs on 1 cm length of stem side); terminal leaflet of primocane leaves with short petiolule (as long as 20–25% of its lamina length), regularly grossly serrate. ........................................................................................................................ R. chaerophylloides Sprib.

5b Primocane stems with more than (15–)20 stalked glands on 1 cm length of stem side, with scattered hairs; terminal leaflet of primocane leaves with longer petiolule (as long as 25–38% of its lamina length), indistinctly periodically (double) and more finely serrate ............................................................................................................................................................................................... 6

6a Primocane stems round to obtusely angled, with 6–10(–14) prickles per 5 cm of stem length, prickles 5–6(–7) mm long, and with 20–30 stalked glands per 1 cm length of stem side; primocane leaves with scattered hairs above (20–40 per 1 cm 2 of leaf surface); sepals often embracing collective fruit; styles greenish or reddish. – Apex of terminal leaflets usually 15–25 mm long .................. .................................................................................................................................................................... R. josholubii H.E.Weber

6b Primocane stems usually distinctly angled, with 11–20(–28) prickles per 5 cm of stem length, prickles (2–)2.5–4(–4.5) long, and with distinctly more (numerous) stalked glands; primocane leaves glabrous above or with few hairs near margins; sepals usually reflexed after anthesis; styles red-violet. – Apex of terminal leaflets usually 12–17 mm long ........................................................... .................................................................................................................................. R. violaceifrons P. Havlíček, Trávn. et Velebil