Monographs Details: Senna ruiziana var. micrandra H.S.Irwin & Barneby
Authors:Howard S. Irwin, Rupert C. Barneby
Authority: Irwin, Howard S. & Barneby, Rupert C. 1982. The American Cassiinae. A synoptical revision of Leguminosae tribe Cassieae subtrib Cassiinae in the New World. Mem. New York Bot. Gard. 35, part 1: 1-454.
Description:Variety Description - Characters as given in key and diagnosis.—Collections: 2. [Key: "Fls small, the petals ±7 mm; anthers 2.8-4 mm, almost beakless; s.-e. Peru (Cuzco) and Bolivia (lat. 13-17°S)."]

Distribution and Ecology - Wooded hillsides and river banks in the monte formation, 700-1800 m, e. foothills of the Andes drained by Rios Madre de Dios and Beni in lat. 13-17°S, from Cordillera de Carabaya in Cuzco (prov. Paucartambo and Quispicanchis), Peru to Las Yungas in La Paz, Bolivia.—Fl. (in Peru) II—III.

Discussion:The two Bolivian collections on which we base var. micrandra were identified by Rusby (in herb.) as Cassia affinis Benth., an obvious mistake corrected in manuscript by Britton, who proposed to describe them as a new species of Chamaefistula, using the epithet boliviensis under which duplicates may possibly still be filed in some herbaria. The plant is clearly very close to genuine S. ruiziana of the Ecuadorean and Peruvian sources of the Amazon, and until the ripe fruit is secured we shall inevitably be somewhat uncertain of its status in relation to that species. It appears, however, from flowering material to differ principally in the slightly smaller flower, especially in the very small, almost beakless anthers. The young forming pod of Vargas 15197 from Cuzco (MO) is less than two centimeters long, and the ripe fruit must surely be smaller than that usually encountered in var. ruiziana. The vesture of young stems and inflorescence in the Bolivian material is denser and looser than that of other specimens, but the Peruvian is unexceptional in this regard.
Distribution:Cusco Peru South America| La Paz Bolivia South America|