Rosa in Manitoba
Delimiting Species Boundaries in Rosa Sect. Cinnamomeae (Rosaceae) in Eastern North America
SIMON JOLY and ANNE BRUNEAU
Systematic Botany (2007), 32(4): pp. 819–836
https://www.webdepot.umontreal.ca/Usagers/jolysi/MonDepotPublic/jolylab/pdf/Joly&Bruneau_2007_SystBot.pdf
1. Hypanthium glabrous........................................................................................... 2
2. Long and straight prickles present throughout the stems..................................... R. acicularis (MB)
2. Prickles absent from the stems or, if present, either short (bristles) or curved........................ 3
3. Infrastipular prickles stout and broad-based..........................................R. virginiana
3. Infrastipular prickles absent or not especially stout or broad-based............................. 4
4. Generally fewer than 2 hairs per mm2 on the abaxial leaf surface;
infrastipular prickles always absent on new stems;
bristles always present on new stems;
leaflets from 7 to 9 per leaf..................R. arkansana (MB)
4. Generally more than 2 hairs per mm2 on the abaxial leaf surface;
infrastipular prickles either present or absent on new stems;
bristles generally absent on new stems;
leaflets from 5 to 7 per leaf....R. blanda (MB) includes R. woodsii
1. Hypanthium with glands . .................................................................... 5
5. Bristles present on new branches............................................................ 6
6. Hairs present on the abaxial surface of the terminal leaflet...................................... 7
7. Infrastipular prickles present...................................................R. carolina
7. Infrastipular prickles absent . .................................................R. arkansana (MB)
6. Hairs absent on the abaxial surface of the terminal leaflet.................................R. nitida
5. Bristles absent on new branches............................................................. 8
8. Width of the terminal leaflet less than 9 mm . . ........................................R. foliolosa
8. Width of the terminal leaflet more than 9 mm . .............................................. 9
9. Hypanthium typically with more than 86 glands;
terminal leaflet oblong,
generally with more than 20 small teeth per margin..........................................................R. palustris
9. Hypanthium typically with fewer than 86 glands;
terminal leaflet ovate, elliptic or obovate,
generally with fewer than 20 teeth per margin..................................................... 10
10. Bristles absent on new stems;
auricles more than 3.8 mm long;
stipules more than 1.1 mm wide;
infrastipular prickles stout, broad based, and often curved......................R. virginiana
10. Bristles present or absent on new stems;
auricles less than 3.8 mm long;
stipules less than 1.1 mm wide;
infrastipular prickles slender and not especially broad based or curved ..............R. carolina
Glossary
Hypanthium = a cuplike or tubular enlargement of the receptacle of a flower, loosely surrounding the gynoecium or united with it (the thing that becomes the outside of the rose hip)
glabrous = smooth, hairless
glands = a plant structure which secretes one or more products. This may be located on or near the plant surface and secrete externally, or be internal to the plant and secrete into a canal or reservoir.
infrastipular - at the base of a node - on a stem the place where a bud occurs
auricle - small ear-like projection from the base of a leaf or petal.
abaxial - the underside
Comentarios
from comments on this observation by lallen https://inaturalist.ca/observations/69941745
"not an expert either, but here's my take on this. First, usually both acicularis and woodsii have larger awl-shaped prickles on the stems, although woodsii usually has also has an obvious pair of these larger prickles just below nodes (called an infrastipular prickle). Both can have fruits that are round to urn-shaped. Woodsii more usually roundish, acicularis more usually oblong, but not a good character to rely on. The character that seems the most reliable to me is the level of prickles on the uppermost, young stems. A "good" woodsii has smooth, shiny, chestnut brown young branches. There will be the occasional prickle, BUT (usually) no acciculi (thin, needle like bristles). Aciclaris has both. So this one, with the prickles and bristles on the upper branches, leans to the acciularis side of things, keeping in mind that these 2 species also hybridize!"
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