This widespread southeastern taxon could include most of the old-field blackberries in Ky., but there has been much confusion with the more northern pensilvanicus group; argutus is combined with many other taxa under pensilvanicus in FNA 9. Typical argutus has been considered to differ from these other taxa in its relatively narrow leaflets (usually widest above middle on primocanes), with simple sharp-serration, the teeth up to 3-6 mm deep (versus doubly serrate, the teeth up to ca. 2-4 mm deep). Typical pensilvanicus has doubly serrate leaves (like most of the extra taxa listed below), but generally broader leaflets and broader petals than argutus. Records mapped here with argutus include the following closely related taxa (or perhaps transitions to pensilvanicus): R. betulifolius Small (BREC), R. immanis Ashe (JEFF, LESL), R. jugosus Bailey (BULL, JESS, MONT, MCRE, ROWA), R. louisianus Berger (BREC, CLIN, MCRE, POWE), R. suus Bailey (BRAC, CAMP, FAYE), and R. arvensis Bailey (BREC, MONT, LESL). This complex will be studied further when M. Medley's colls. are processed at APSC. Some of these names have been considered synonyms, especially under immanis; some may represent transitions from argutus to pensilvanicus and its allies, or have unsettled affinity (F, St; Widrelechner 1998). R. arvensis may be relatively distinct, with lower leaf surfaces whitish to glaucous and covered by short hairs.