Pleurothallis, abbreviated Pths in horticultural trade, is a genus of orchids commonly named bonnet orchids. The genus name is derived from the Greek word 'pleurothallos', meaning 'riblike branches'. This refers to the rib-like stems of many species. This was a huge genus, which used to contain more than 1,200 species - the second largest in the Orchidaceae after Bulbophyllum. In 2004, it decreased by more than half when many species were moved into new genera.