The Lentibulariaceae are a large herbaceous group of carnivorous plants, well represented in both temperate and tropical regions, and occupying aquatic, semi-terrestrial and epiphytic habitats.

Distribution. The family has a nearly cosmopolitan distribution, ranging from subarctic conditions to tropical savannas and forests. The largest genus, Utricularia (Bladderworts), is widely distributed and extremely diverse, occurring as submerged aquatics, semi-terrestrial in wetlands and seasonally wet habitats, and as epiphytes in montane tropical rain forests and cloud forests. Pinguicula (Butterwort) is primarily a warm-temperate genus, extending through the tropical zone in the Andes Mountains, with P. antarctica extending south to Tierra del Fuego; a few species, such as P. vulgaris, have a boreal distribution. Genlisea is a tropical genus, with 11 species known from the Neotropics and 8 species in tropical Africa.

Family classification. The Lentibulariaceae is a well defined family of three carnivorous genera, each with a distinct trap mechanism. The family appears to be derived from the closely related Scrophulariaceae. The genus Utricularia has been subdivided into two subgenera, the diverse subgenus Utricularia and the subgenus Polypompholyx, a group consisting of three Australian species, characterized by a four- rather than two-parted calyx, and sometimes has been treated as a segregate genus. The extremely diverse subgenus Utricularia is further subdivided into 33 sections.

Number of genera and species. According to recent taxonomic treatments, the Lentibulariaceae, consist of three genera and approximately 280 species. The genus Utricularia accounts for most of the diversity, with about 215 species, Genlisea with about 20 species and Pinguicula with about 45 species.

Features of the family. Lentibulariaceae are perennial and annual herbaceous, carnivorous plants of aquatic and wet habitats. Species of Utricularia and Genlisea are rootless, free-floating (aquatic species), or often anchored in the wet sandy or peaty substrate by rhizoids or stolons (semi-terrestrial species), or anchored in a mossy substrate (in epiphytic species); a number of species also bear tubers, apparently critical for surviving periods of dessication. Leaves are borne in rosettes in Pinguicula, Genlisea and some Utricularia. Many Utricularia have small, somewhat petiolate, narrowly linear to somewhat obovate, thin lamina; the submersed aquatic species have highly divided, capillary segments. Flowers are borne solitary on a scape (Pinguicula) or in few- to many-flowered scapose racemes, subtended by bracts and bracteoles (basifixed or peltate). Flowers are bisexual, zygomorphic, the calyx 2(-4)- or 5- lobed. The corolla is sympetalous and 2-lipped, with the lower lip spurred (sometimes short and saccate), and often with a conspicuous palate at the throat of the corolla. The androecium consists of 2 epipetalous stamens, with 2 staminodes sometimes present. The pistil is 2-carpellate, the ovary superior, unilocular, with 1-numerous ovules on a free-central placenta. The fruit is a capsule, dehiscing by 2-4 valves, circumscissiley, or by irregular splitting, or, in a few, indehiscent.

Natural history. The family is especially interesting because of the presence of carnivorous traps. The traps are quite varied. In Pinguicula the trap mechanism is passive, consisting of a rosette of leaves covered with stalked glandular hairs that trap insects and sessile glands that secrete digestive enzymes. In Utricularia the plants bear numerous bladders in which the digestive processes occur. The trap consists of a stalked, globose sac-like structure with a trap door at the entrance. Around the trap door are bristles that function as trigger hairs. The trap is set by absorptive hairs within the bladder creating a vacuum, and if the trigger hairs are touched, the extremely rapid rush of water into trap sucks the animal inside. There is considerable variation in trap morphology, typically reflective of taxonomic sectional groups. In Genlisea the traps are tubular or pitcher-like leaves, with positive geotropic growth, thus appressed into the ground. The trap is a complex structure consisting of a footstalk, a hollow bladder, a tubular neck, and two twisted arms, with the inner epidermis of the trap containing hairs and glands. It is not clear whether the trap functions as a passive organ, with unidirectional movement and working like an "eel trap" or "lobster pot", or is an active trap, with a suction mechanism.

At first glance, the epiphytic species of Utricularia in Neotropical rain and cloud forest habitats are likely to be mistaken for orchids, with which they may grow. The 2-lipped, zygomorphic flowers tend to be quite showy, the leaves can be fairly large and somewhat leathery, and tubers, reminiscent of pseudobulbs of the orchids, allow them to survive periods of desiccation during the dry season--hardly typical of the temperate botanist's concept of the genus. These species belong to Section Orchidoides, a Neotropical group consisting of 9 species, centered primarily in the Andes and ranging into the mountains of Central America.

Economic uses. Because of the enormous interest in carnivorous plants as novelty plants, there are a number of plant societies in various countries focusing attention on the Lentibulariaceae and other carnivorous groups. A number of species are popular for growing and seeds or plants can be readily obtained by plant enthusiasts.

References. Crow, G. E. 1992. The genus Utricularia (Lentibulariaceae) in Costa Rica. Brenesia 38:1-18. Fromm-Trinta, E. 1979. Revisao do gênero Genlisea St. Hil. das regioes sudeste e sul do Brasil. Rodriguesia Vol. 31, No. 49: 17-139, 35 figs. Godfrey, R. K. and H. L. Stripling. 1961. A synopsis of Pinguicula (Lentibulariaceae) in the southeastern United States. Heslop-Harrison, Y. 1978. Carnivorous Plants. Scientific American 238(2): 104-115 Lloyd, F. E. 1976. The Carnivorous Plants. Waltham, Mass. Reut, M. S. 1993. Trap structure of the carnivorous plant Genlisea (Lentibulariaceae). Bot. Helv. 103: 101-111. Taylor, P. 1989. The genus Utricularia - a taxonomic monograph. Kew Bull. Add. Ser. 14: 1-724. Taylor, P. The genus Genlisea. Carnivorous Plant Newsletter 20: 20-35.

Prepared for: Families of Neotropical Flowering Plants (Andrew Henderson, editor). In press. New York Botanical Garden.

26 January 1998