Our speaker for July was Helen Milner whose subject for the evening was Pleurothallids, focusing
on the genus Restrepia. This genus named in honour of Don Jose Restrepo is made up of some 50 species.
Helen’s PowerPoint presentation began with a description of their distribution in South America,
being found in the Andes and Venezuela with some into Central America and up to southern
Mexico. Their typical habitat is in wet temperate montane forest where they grow at altitudes
between 1500 – 3500 metres among mosses, ferns and bromeliads. They are small epiphytic or
lithophytic orchids without pseudobulbs, possessing thick leaves and fine aerial roots. The flowers, which are carried on a peduncle originating from the back of the leaf show considerable difference to many orchid flowers. The long dorsal sepal has a club like tip, and the fused lateral sepals (synsepals) show a wide range of colours, often striped or spotted, according to the species. The lateral petals are also elongated with thickened tips and the labellum is shows the same variations in colour and marking. These were shown in many fine illustrations of the species.
Perhaps the most intriguing illustrations were images at very high magnification from a scanning
electron microscope of the structure of the labellum. They showed two structures called calli which focus light by reflection to guide pollinators to the column, and also the montane structure of the labellum which helps pollinating insects to grip the surface of the lip. Cross pollination is essential as self pollination in the wild results in sterile seeds.
The line of major distribution of the genus along the Andes is also a hot spot for deforestation,
endangering the genus. The pressures put on it include changes in land use, road construction and eco-tourism. This Helen compared with the pressures on orchid growing, with fewer commercial growers and major collections declining making species plants more difficult to obtain putting pressure on ex situ conservation.
The evening concluded with Helen taking questions on Restrepia culture and orchid conservation.