This species which is one of the smallest of the genus Mimosa, is found in the prairies around Rio-Janeiro. Its stem is feeble, rather woody, ramose, pubescent above and covered with very sharp prickles. The leaves are bipinnate, the pinnæ being three- or four-paired, with small, linear folioles, which close at the least contact; there are from 6 to 12 on each side of the spike. The flowers are small, sessile, forming pretty silky tufts of a violet color. The fruit is somewhat triangular, flattened, covered with long and stiff hairs, and surrounded by a persistent pericarp, divided in two capsules, each of which contains one seed. _First day._—1. Twitching of the arm, which extends even to the chest. Smarting pain in the legs, with lameness of the knee. Headache, with weakness of the stomach. Stomach-ache after breakfast. 5. Drowsiness. Flatulence and rumbling in the bowels. Yawning. Ptyalism. Shuddering. 10. Trembling of the legs. Lancinations in the legs and hands. Sneezing. Coryza and discharge from the nose. Inflamed eyes. 15. Papulæ on the left leg. Constipation. Depression of spirits. _Second day._—Frequent waking at night. Dry cough in the morning. 20. Stomach-ache after breakfast. Vertigo. Halo around the candle-light. Numbness of the hands. Stiffness of the bends of the knees. 25. Sense of heat in the head. The head seems larger than usual. Yawning. Indolent indifference. Flatulent colic in the evening. 30. Frequent stools, with colic. Papulous excrescence of the size of an almond on the right leg, painful and itching. The same swelling at the instep. Drowsy in the evening. Difficult breathing. _Third day._—35. Inflammatory swelling of the scrotum. Itching of the eyes. Pressure at the nape of the neck and the right temple. Papulous excrescence at the tendo-Achillis. Dimness of vision. 40. Pain in the sides of the head. Diarrhœa. _Fourth day._—Swelling of the left ankle, with redness, tension and lancinations. The excrescences on the leg disappear; similar ones appear on the left arm. Easy stool. 45. Numbness of the arm and right hand, passing off when moving the parts. The left eye becomes inflamed. Want of breath. _Fifth day._—Bleeding of the gums. The papulæ disappear. 50. Acute lancinations, now in the legs, then in the arms. Violent lancinations in the back as from a penknife. Drowsy in the evening, with frequent waking at night. _Sixth day._—Inflammatory swelling of the left hand. Shuddering. _Eighth day._—55. Flatulence. Diarrhœa. _Tenth day._—Diarrhœa. Whizzing in the ears. ARRANGEMENT ACCORDING TO HAHNEMANN. HEAD, &c.: 1. Vertigo. Indifference. Depression of spirits. Pain in the sides of the head. 5. Headache, with weak stomach. Heat in the head. The head feels as if swollen. Coryza, fluent. Itching of the eyes. 10. Dimness of sight. The left eye is inflamed. Inflamed eyes. Whizzing in the ears. Bleeding of the gums.