Aa

What is Aa?

The genus Aa comprises a group of orchids within the Orchidaceae family, notable for their unique characteristics and habitat. These plants are typically found growing terrestrially in cold environments, often near the snowline in the Andes mountain range, and also occur in Costa Rica. They have a strong association with small streams, usually growing in their vicinity.

Morphology and Characteristics

Species within the Aa genus are distinguished by their elongated inflorescence, which emerges from a basal rosette of leaves. The inflorescence terminates in a small flower that is white and non-resupinate. A defining feature of the Aa flower is its lip, which is notably fringed and hood-shaped. This unique floral structure is complemented by a pungent smell emitted by the flower, a scent that serves to attract flies, which are believed to be their primary pollinators.

Taxonomic History

The classification of Aa has seen some fluctuation. Historically, species within this genus have often been included under the broader orchid genus Altensteinia. The first scientific description of a species now recognized as belonging to the genus Aa was made in 1815 by Karl Sigismund Kunth, who initially named it Ophrys paleacea and later Altensteinia paleacea. Heinrich Gustav Reichenbach formally separated Aa from Altensteinia in 1854, establishing it as a distinct genus. However, Reichenbach later revisited this decision, renaming it Altensteinia again. It was not until 1912 that Rudolf Schlechter reinstated the name Aa, a change that gained more significance as additional species were discovered. The genus name 'Aa' is notable for its position as the first in alphabetical order, a characteristic likely intentional by its namer.