An irritable labellum is characteristic of Acostaea Schltr., Porroglossum Schltr., and the presently proposed monotypic genus. In each of the three genera a diferent mechanism has developed independently to cause the lip to snap suddenly upward to the under surface of the column, ostensibly to force the pollinator against the column. Physiological experiments have not been carried out satisfactorily to explain the exact cause of the actions which are precipitated by some tactile event. Obviously a different set of circunstances is responsible for the action in each of the three genera. After a period of time, the lips in all three genera resume their exposed positions.