Barnhart, John H. 1916. Segregation of genera in Lentibulariaceae. Mem. New York Bot. Gard. 6: 39-64. f. 1-25.
Lentibulariaceae
Latin Diagnosis - Herbae scaposae terrestres, radicibus fibrosis. Folia rosulata; ascidia nulla. Scapus nudus, uniflorus, circinatus. Calyx 5-lobatus, plus minus 2-labiatus; labium superius 3-lobatum, inferius 2-lobatum. Corolla 5-lobata, plus minus 2-labiata; labium superius 2-lobatum, inferius 3-lobatum; tubus infra saccatus atque in calcar nectariferum contractus. Antherae subglobosae. Capsula bivalvata. Semina numerosa, oblonga, reticulata.
Distribution and Ecology - About 30 species, widely distributed throughout the northern hemisphere, especially in America, and ranging southward along the Andes to Patagonia.
Species typica, Pinguicula vulgaris L.
Four marked corolla-types may serve to distinguish as many subgenera, or perhaps genera. Of these, the most distinct is Temnoceras.
A. ISOLOBA (Raf. pro gen.). Corollae lobi subaequales et subaequaliter divergentes; calcar abrupte contractum et cum tubo angulum validum formans.
B. PIONOPHYLLUM A.DC. Corollae limbus obliquus; lobi 2 superiores erectiores et plus minus coaliti, 3 inferiores explanati et plus minus coaliti; tubus in calcar gradatim transiens.
C. ORCHEOSANTHUS A.DC. Corolla profunde 5-partita itaque tubo subnullo; calcar pendens, lineare.
D. TEMNOCERAS (subgen. nov.). Corolla profunde bilabiata; labium superius bidentatum, inferius divergente trilobatum; calcar subcylindricum.
Isoloba comprises 4 species in the southeastern United States, and about 6 in tropical America; there is only one in the Old World, the little-known P. lusitanica L. The subgenus Brandonia differs only by its yellow corollas, and seems unworthy of taxonomic recognitioni Some of the species of Isoloba have a prominent acicular or even clavate palate, included in the throat, but in other species the palate is much less distinct, while in some it is essentially obsolete.
Pionophyllum comprises about 15 species, mostly European, some of them ranging to the mountains of central Asia and northern Africa, or to the northern parts of North America; while a few are found in tropical America, and one as far south as Patagonia.
Orcheosanthus includes about 6 species, apparently, but future study may show that the number is less, or that the fragmentary material now preserved in herbaria represents a much larger number. The range of variation is enormous, but how much is seasonal, how much individual, and how much of taxonomic importance, is at present mere guesswork. The group is wholly confined to Mexico.
Temnoceras is based upon a single described species, a small one of Mexico and Central America, Pinguicula crenatiloba. Probably it will eventually be segregated into several species, but the material now available is insufficient to accomplish this in a satisfactory manner. The corolla-sinus is so deep that it extends beyond the corolla-base and the lower lip is connected with the upper one only by the spur; hence the name, which signifies cleft spur.