This tetrapoid (2n = 32) occurs mostly in or near the Ozark region, but appears to be adventive in some eastern states (Pennell 1935, GC, K, FNA 17). It has been reported from Ky. (M, FNA 17), but no colls. have been located here; the report of Mohlenbrock et al. (1966) from GRAV (SIU) was based on misidentified digitalis. P. tubaeflorus is known from nearby in w. Tenn. (Ch+, K). Although distinctive, it can be confused with alluviorum (especially) or digitalis; and further study of colls. filed under these names is needed. P. tubaeflorus differs (F) in its corollas minutely glandular-puberulent within (versus glandless but with few to many short simple bristles), leaves entire or nearly so (versus entire to sharply serrate), and stems glabrous (versus glabrous or hairy, at least in lines). Also, as stated by FNA 17: "Fruiting specimens of P. tubaeflorus often are misidentified as P. digitalis; the former can be distinguished by its more cylindric inflorescences with erect peduncles and smaller capsules."