Genus of flowering plants
Aa is a genus of plants of the family Orchidaceae.
Species in this genus can be found growing terrestrially in cold habitats near the snowline in the Andes and also in Costa Rica; they are usually found close to small streams. The elongated inflorescence grows from a basal rosette of leaves, terminating in a small white non-resupinate flower. This lip is fringed and hood-shaped. The flower gives off a pungent smell that attracts flies. This genus has often been included in the orchid genus "Altensteinia".
The first scientific description of a species of this genus was made in 1815 by Karl Sigismund Kunth, naming it first "Ophrys paleacea" , and later "Altensteinia paleacea". In 1854 Heinrich Gustav Reichenbach separated "Aa" from "Altensteinia", to include two species "Aa argyrolepis" and "Aa paleacea". The genus name apparently was rendered by the author to always appear first in alphabetical listings. Another – disputed – explanation, is that Reichenbach named this genus after Pieter van der Aa; the printer of the Dutch botanist Paul Herman's "Paradisus Batavus". A few years later, Reichenbach reviewed the name of the genus and named it again "Altensteinia". Finally in 1912 Rudolf Schlechter switched the name again to "Aa", as more species were being discovered making the new name more significant.
Species.
The following species of "Aa" are accepted
Synonyms: 
References.
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