Mimosa quadrivalvis var. angustata (Torr. & A. Gray) Barneby

Littleleaf sensitive-briar (scientific name Mimosa microphylla) is a small, woody vine native to the southeastern corner of the United States.It grows in dry woodlands, forests, sandhills and disturbed areas with well drained soils.Its distribution includes Kentucky, Illinois, Virginia, the Carolinas, Georgia, Florida, Alabama, and west as far as Texas.Littleleaf sensitive-briar belongs to the legume family (Fabaceae).Its green, prickly stems sprawl along the ground or wind over other small plants, growing to about 6 feet (2 m) long.

The leaves of littleleaf sensitive-briar are each made up of many (6-16) sub-leaves, called pinnae.These branch off around the leaf’s main shaft.In turn, each pinnae is itself made up of (20-32) tiny leaflets, lined up around a smaller midvein.The overall effect is that the leaves have a feathery look. When it blooms in mid-June, the vine resembles a colorful string of pom-poms.The thumbnail-sized flowerheads are hot-pink balls made up of many tiny spiky flowers sticking out from the center.A dot of yellow pollen at the tip of each tiny flower's anther gives the flowerhead a striking look.

Mimosa microphylla has small, inconspicuous, but sharp thorns along its stem and leaf veins.The seeds grow in thin, round pods, which are also covered with spines.When ripe, the pod dries and splits down its length to disperse the row of seeds harbored inside.Birds, such as quail, northern bobwhite, and other seed foragers eat and disperse the seeds.

Like other legumes, Mimosa microphylla grows nodules on its roots to house mutualistic nitrogen-fixing bacteria.The plants return this nitrogen to the soil, thus improving the soil in which they grow.

Littleleaf sensitive-briar belongs to a group of plants called sensitive plants: they are sensitive to touch or movement.When a leaf is disturbed, tapped, or rubbed, or even if it senses vibrations from disturbance of the next leaf over, the little leaflets quickly fold in against each other along their midrib.At the same time, the midribs curl down past the main stem, lowering the folded up leaves out of the way.

It is believed that sensitive plants curl up their leaves to protect from herbivory.By folding up, the leaves almost disappear, and the sharp thorns along the stems stand out, deployed and unobstructed.At night, the leaves of little-leaf sensitive briar fold in by themselves; since they cannot photosynthesize at night anyway, they might as well have their guard up against predators.Ungulates such as white-tailed deer and cattle do not commonly graze on M. microphylla.The gopher tortoise, however, readily eats it as a large part of its diet, as do snails and some plant-eating insects.

(Eisner, 1981; Flora of the Southeast 2005; Hilton 2004; LBJ Wildflower Center 2015; Knapp 2010; Miller and Miller 2005)

Leptoglottis angustisiliqua Britton & Rose, sp. nov
Glabrous throughout; stem slender, up to 1 m. long or longer, rather distantly prickly. Stipules 2-4 mm. long; petioles and leaf-rachis very slender, prickly; petioles 2.5-3.5 cm. long; pinnae 3-6 pairs; leaflets 7-16 pairs, linear-oblong, 2.5-3.5 mm. long, inconspicuously veined, obtuse or acutish; peduncles loosely prickly, in fruit 3-5 cm. long; legume .subterete, not densely prickly, 6-7 cm. long, only about 2 mm. thick, its slender beak about 7 mm. long.
Pinelands of southern Florida, and in Texas. Type from Brogdon Hammock, Dade County, Florida, June 19, 1915, Small & Mosier 6349.

Leptoglottis chapmanii Small
Schrankia angustata brachycarpa Chapm. Fl. S. U. S. ed. 2, 116. 1883. Not Schrankia brachvcarpa Benth. 1840.
Glabrous; stems slender, 6-10 dm. long, armed with short prickles. Stipules 2-3 mm. long; petioles and leafrachis very slender, prickly; petioles about 3 cm. long or shorter; piimae 3-6 pairs; leaflets 8-12 pairs, linear, obtuse or acutish, 3-4 mm. long, the midvein delicate, otherwise veinless; peduncles prickly, very slender, 2—4 cm. long; legume subterete, densely prickly, 3-6 cm. long, about 4 mm. thick, nearly beakless.
Type locality: Dry pine barrens, Florida. Distribution: Florida to North Carolina and Louisiana.

Leptoglottis microphylla (Dryand.) Britton & Rose
Mimosa Inisia Walt. Fl. Car. 252, 1788. Not L. 1753.
Mimosa microphylla Dryand.; J. E. Smith, Insects Georgia 2: 123. 1797.
Mimosa horridula Michx. Fl. Bor. Am. 2; 254. 1803.
Schrankia nnciitata Willd. Sp. PI. 4: 1043. 1806.
Schrankia am^uslata Torrev & Gray, Fl. N. Am. 1: 400. 1840.
Schrankia Inl.ua Trel.; Branner & Coville. Rep. Ark. Geol. Surv. 1888<: 178. 1891.
Schrankia horridula Chapm. Fl. S. U. S. ed. 2, Suppl. 2, 683. 1892.
Morongia uncinata Britton, Mem. Torrey Club 5: 191. 1894.
Morongia angustata Britton. Mem. Torrey Club 5: 191. 1894.
Leptoglottis Intsia Rydb. Bot. Surv. Neb. 3: 33. 1894.
Schrankia horridula angiilaris Chapm. Fl. ed. 3, 127. 1897.
Moroni;ia horridula Heller. Cat. N. Am. PI. 5. 1898.
MoronKKi luirridiila angularis Heller. Cat. N. Am. 5. 1898.
Moronsia microphylla Britton; Britton & Brown, III. Fl. ed. 2, 2: 334. 1913.
Stems glabrous or puberulent, slender, copiously or sparsely prickly, prostrate or decumbent, 6-12 dm. long. Stipules 3-4 mm. long; petioles and rachis slender, prickly; pinnae 3-8 pairs; leaflets 10-17 pairs, linear-oblong, glabrous, 4-6 mm. long, membranous, inconspicuously veined, acutish or obtuse; peduncles very slender, prickly, 2-7 cm. long; legume subterete, glabrous or puberulent, rather densely prickly, 6-14 cm. long, about 3 mm. thick, its beak 6-10 mm. long.
Type locality: South Carolina.
Distribution: Virginia to Tennessee. Florida. Mississippi and Texas.

Perennial, Shrubs, Stems woody below, or from woody crown or caudex, Taproot present, Nodules present, Stems or branches arching, spreading or decumbent, Stems prostrate, trailing, or mat forming, Stems less than 1 m tall, Stems 1-2 m tall, Stems greater than 2 m tall, Trunk or stems armed with thorns, spines or prickles, Stems solid, Stems or young twigs gl abrous or sparsely glabrate, Stems with hooked uncinate hairs or prickles, Leaves alternate, Leaves petiolate, Stipules conspicuous, Stipules setiform, subulate or acicular, Stipules persistent, Stipules free, Leaves compound, Leaves bipinnate, Leaf or leaflet margins entire, Leaflets opposite, Leaflets 10-many, Leaves glabrous or nearly so, Flowers solitary in axils, or appearing solitary, Flowers in axillary clusters or few-floweredracemes, 2-6 flowers, Inflorescences globose heads, capitate or subcapitate, Inflorescence axillary, Flowers actinomorphic or somewhat irregular, Calyx 5-lobed, Calyx glabrous, Petals united, valvate, Petals white, Imperfect flowers present, dioecious or polygamodioecious, Stamens 9-10, Stamens completely free, separate, Stamens long exserted, Filaments glabrous, Filaments pink or red, Style terete, Fruit a legume, Fruit unilocular, Fruit freely dehiscent, Fruit elongate, straight, Fruit oblong or ellipsoidal, Fruit exserted from calyx, Fruit sp iny, bur-like, with hooked bristles or prickles, Fruit beaked, Fruit 3-10 seeded, Seed with elliptical line or depression, pleurogram, Seeds subquadrate, Seed surface smooth, Seeds olive, brown, or black.

Mimosa microphylla, commonly called littleleaf sensitive-briar, is a species of flowering plant in the legume family (Fabaceae). It is a perennial herb native to North America, where it is found primarily in the southeastern United States. Its typical natural habitat is in dry woodlands and forests, although it can also be found in disturbed areas.