This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Erect or climbing shrubs, generally with subterranean rootstocks. Stems commonly prickly. Leaves alternate, odd-pinnate. Stipules adnate to the petiole. Flowers corymbose or solitary, red, pink or white (in our species). Calyx-tube cup-shaped or urn-shaped, constricted at the throat, becoming fleshy in fruit, 5- (rarely 4-) lobed, the lobes imbricated, spreading, deciduous or persistent. Petals 5 (rarely 4), spreading. Stamens ∞, inserted on the hollow annular disk. Carpels ∞, sessile at the bottom of the calyx; ovaries commonly pubescent; styles distinct or united. Achenes numerous, enclosed in the berry-like fruiting calyx-tube. Seed pendulous. [The ancient Latin name of the rose.]
A large genus, the number of species variously regarded, natives of the northern hemisphere. Besides the following, several others occur in the southern and western parts of North America. Type species: Rosa centifolia L.
* Styles cohering in a column; leaflets mostly 3.
** Styles all distinct; leaflets 5-11.
Calyx-lobes persistent, erect on the fruit, or spreading.
Infrastipular spines generally none.
Stems unarmed or nearly so; calyx-lobes erect on the fruit.
Stems armed with numerous prickles.
Leaflets 3-9, often resinous, obtuse at base; flowers solitary; calyx-lobes erect on the
Leaflets 7-11, not resinous, narrowed at base; flowers corymbed; calyx-lobes spreading.
Infrastipular spines commonly present; stems prickly.
Calyx-lobes entire; native western species.
Calyx-lobes, at least the outer ones, deeply incised; introduced specie
Calyx-lobes deciduous, spreading.
Leaflets finely serrate; spines stout, recurved.
Leaflets coarsely serrate.
Stems with scattered prickles or naked; flowers often solitary.
Stems very densely prickly; flowers usually solitary.
Infrastipular spines stout, hooked; introduced wand-like or climbing species
Leaves evergreen; calyx-lobes persistent.