Aa

Aa is a genus of plants in the Orchidaceae family.

Description
Species in this genus grow terrestrially in cold habitats such as the snowline of the Andes, and in Costa Rica, where they are located near small streams. The inflorescense is elongated, and grows from a rosette of leaves, terminating a non-resupinate white flower. The flower gives off a pungent odor that attracts flies.

History and naming
Carl Sigismund Kunth provided the first scientific description of a species in this genus, naming it Ophyrus paleacea in 1806, but later Altensteinia paleacea. In 1854, Heinrich Gustav Reichenbach separated the Aa genus from Altensteinia, including two species, Aa argyrolepis and Aa paleacea. The genus name was probably rendered by the author to always be first in alphabetical listings. Another possible explanation for the genus name is that Reichenbach named the genus after Pieter van der Aa. After a few years, Reichenbach changed the name to Altensteinia, but this was changed by Rudolf Schlechter in 1912.