Aa Rchb.f. 1854, is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of plants belonging to the family Orchidaceae

Orchidaceae

The Orchidaceae, commonly referred to as the orchid family, is a morphologically diverse and widespread family of monocots in the order Asparagales. Along with the Asteraceae, it is one of the two largest families of flowering plants, with between 21,950 and 26,049 currently accepted species,...

.

Species in this genus can be found growing terrestrially

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 in cold habitats near the snowline in the Andes

Andes

The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 and also in Costa Rica

Costa Rica

Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....

; they are usually found close to small streams. The elongated inflorescence

Inflorescence

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

 grows from a basal rosette of leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

, terminating in a small white non-resupinate flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

. This lip is fringed and hood-shaped. The flower gives off a pungent smell that attracts flies

Fly

True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...

. This genus has often been included in the orchid genus Altensteinia

Altensteinia

Altensteinia is a genus of orchid. It is found in the Andean region of South America and has seven accepted species.- List of species :* Altensteinia boliviensis Rolfe ex Rusby * Altensteinia citrina Garay...

.

The first scientific description of a species of this genus was made in 1815 by Karl Sigismund Kunth, naming it first Ophrys paleacea Kunth (1806)., and later Altensteinia paleacea. In 1854 Heinrich Gustav Reichenbach

Heinrich Gustav Reichenbach

Heinrich Gustav Reichenbach was an ornithologist, botanist and the foremost German orchidologist of the 19th century...

 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 Heinrich Gustav Reichenbach

Heinrich Gustav Reichenbach

Heinrich Gustav Reichenbach was an ornithologist, botanist and the foremost German orchidologist of the 19th century...

 named this genus after Pieter van der Aa

Pieter van der Aa

Pieter van der Aa was a Dutch publisher best known for preparing maps and atlases. Some of his most popular maps were of the African continent, detailing locations such as Morocco and Madagascar....

; 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

• Aa achalensis Schltr. 1920 (Argentina)
• Aa argyrolepis Rchb.f. 1854 (Colombia to Ecuador)
• Aa calceata (Rchb.f.) Schltr. 1912 (Peru to Bolivia)
• Aa colombiana Schltr. 1920 (Colombia to Ecuador)
• Aa denticulata Schltr. 1920 (Colombia to Ecuador)
• Aa erosa (Rchb.f.) Schltr. 1912 (Peru)
• Aa fiebrigii (Schltr.) Schltr. 1912 (Bolivia)
• Aa gymnandra (Rchb.f.) Schltr. 1912 (Bolivia)
• Aa hartwegii Garay 1978 (Ecuador; Colombia; Venezuela)
• Aa hieronymi (Cogn.) Schltr. 1912 (Argentina)
• Aa inaequalis (Rchb.f.) Schltr. 1912 (Peru to Bolivia)
• Aa leucantha (Rchb.f.) Schltr. 1920 (Colombia to Ecuador)
• Aa lorentzii Schltr. 1920 (Argentina)
• Aa macra Schltr. 1921 (Ecuador)
• Aa maderoi Schltr. 1920 (Venezuela; Colombia; Ecuador)
• Aa mandonii (Rchb.f.) Schltr. 1912 (Peru to Bolivia)
• Aa matthewsii (Rchb.f.) Schltr. 1912 (Peru)
• Aa microtidis Schltr. 1922 (Bolivia)
• Aa nervosa (Kraenzl.) Schltr. 1912 (Chile)
• Aa paleacea (Kunth) Rchb.f. 1854 (Costa Rica to Bolivia)
• Aa riobambae Schltr. 1921 (Ecuador)
• Aa rosei Ames 1922 (Peru)
• Aa schickendanzii Schltr. 1920 (Argentina)
• Aa sphaeroglossa Schltr. 1922 (Bolivia)
• Aa trilobulata Schltr. 1922 (Bolivia)
• Aa weddeliana (Rchb.f.) Schltr. 1912 (Peru to NW Argentina)

External links

• Pictures of Chilean Aa nervosa orchid