I got these photos of Satyrium nepalensis from the botanist Bhakta Bahadur Raskoti in Katmandu who has just published a new book presenting “The Orchids of Nepal”. He wrote me that there are some species of orchids in Nepal which are flowering in pink and rarely in white. In addition to Satyrium nepalensis those are Spiranthes sinensis, Rhynchostylis retusa or Anthogoneum gracile. Spiranthes sinensis reminds of the European Spiranthes spiralis, its standard form shown in the book of Bhakta Bahadur Raskoti has dark pink sepals and petals and a white labellum. “Orchids of Nepal” presents 302 species with more than 900 photos. Among them 14 species are new reports for the orchid flora of Nepal.

It seems to be a good year for Orchis militaris – the meadows in biking distance from Frankfurt are full with violet inflorescences. And this time, in the fifth year of continous observation, there is a second albiflora form of an Orchis militaris, just ten meters away from the place of the first plant. It has a height of 20 cm, a rosette of three leaves and about ten flowers. The reproduction of albiflora forms is difficult, since the DNA sequence responsible for the lack of flower pigments is recessive, but here it has obviously happened. The first albiflora plant is about 30 cm tall, with five foliage leaves and about 25 flowers:

Last year, about 800 Anacamptis morio have been flowering in the Rheingau region, west of Wiesbaden – among them five with white flowers. This year, only ten plants are flowering, a decrease of 99 percent. And there wasn’t any Anacamptis morio f. albifora on the meadow. Hiking around the neighboring woods I met a huntsmen who was sawing logs. He told me that wild hogs are probably the cause why the orchids have been diminished to such a great extent. The long lasting winter has done its part to prompt the hogs searching for orchid roots. On the adjacent meadow I’ve found about 20 Orchis mascula in the beginning of flowering.

… develop white flowers while their species is supposed to have coloured flowers. This Gentiana germanica, found at Seiser Alm in the Dolomite Alps, is an example.

The plant at the right side has flowers without pigments (anthocyanins). It may be viewed as “Gentiana germanica albiflora”, as Ferdinand Schur has noted in his article “Beitraege zur Flora von Wien” (Oesterreichische Botanische Zeitschrift vol. 11/1860). The correct name should be Gentiana germanica f. albiflora.

Another example found this year in the Swiss region of Aargau is Ajuga reptans f. albiflora which has acquired some horticultural importance.

But neither the Gentianaceae nor the Labiatae (the family of the genus Ajuga) could be viewed as a family with a certain tendency towards developing white flowers – as it is the case with orchids. Maybe another family with an albiflora disposition are the Cactaceae. A charming web gallery of albiflora cacti has been set up by Gerd Weiss presenting more than 50 species.

“The palette of colors in nature is almost infinite”, says the botanist Hilke Steinecke of the Palmengarten in Frankfurt. There, this palette is displayed in an exhibition which can be visited until November 1st. The exhibition also explains the role of pigments in the colors of flowers and how fertilizing insects see colors.

An interesting demonstration shows the acid sensitivity of anthocyanins. When a drip of vinegar is placed on the violet flower of  Ipomoea, its color changes to pink. “In an acid milieu many anthocyanins are rose-pink, in an alkaline milieu blue”, as it is stated in the catalogue. This phenomenon could also explain the color variations of Nigritella nigra ssp. rhellicani in the Dolomite Alps – these occur especially in a region with rather acid soil.

The females of this crab spider (Misumenia vatia) can change their colour depending on the colour of the flower where they sit and wait for a prey. On a white flower they have a white body, on yellow flowers it is changed to an intense yellow (right, photo: Olaf Leillinger). Thus, the albiflora form of Dactylorhiza fuchsii (left, photo: Norbert Griebl) is quite a convenient place to hunt insects – the standard purple colour of this orchid would not fit her camouflage strategy. The spider changes its colour by secreting a yellow pigment into the outer cell layer of its body.While sitting on white flowers, this pigment is transported into lower layers. The colour change from white to yellow takes between 10 and 25 days, the reverse about six days.

Today, 200 years ago, Charles Darwin was born – his vivid interest in varieties of animals and plants has led him to the insights of evolution: Species are not created once and forever but are rather the result of a process, which is partly still continuing. Especially the relatively young family of orchids is still in the midst of its development, and nature is trying to go new ways. One of them are colour variations like white orchids.

In his book about “The various contrivances by which orchids are fertilised by insects” (1862, 2. Auflage 1877), Darwin studied the structure of orchid flowers in relation to their pollinators. About Platanthera chlorantha (which he called Habenaria chlorantha) he wrote, that they are pollinated by moths – due to their long spur filled with nectar and an intense scent at night: “The remarkable length of the nectary, containing much nectar, the white colour of the conspicuous flower, and the strong sweet odour emitted at night, all show that this plant depends for it fertilisation on the larger nocturnal Lepidoptera.”(p.85). In a famous forecast Darwin estimated that there must be a pollinator in Madagascar matching the orchid Angraecum sesquipedale which has a spur with a length of 25 cm: “In Madagascar there must be moths with probosces capable of extension to a length of between ten and eleven inches!” (p. 198). In 1903, 41 years later, the appropriate butterfly was found, Xanthopan morgani.

The shipment took more than a month but now the book has arrived from Cornell University Press in Ithaca, New York. It’s really intersting, the Illustrated Dictionary of Orchid Genera. The authors Peggy Alrich and Wesley Higgins present an overview on all the genera of the family of orchids – from  Aa to Zygostates.

Aa is quite a nice story – this valid taxon was defined by Heinrich Gustav Reichenbach in 1854. One explanation for the unusual name is that Reiuchenbach took the first and the last letter of the related genus Altensteinia in order to be always at the first place of  the compendia – the new reference book demonstrates his success. Another explanation says that Aa with its 27 species in Central and Southern America commemorates the Dutch printer Pieter van der Aa.

The preface states that there are about 850 accepted genera in the world of orchids – but the number described in the book is more than three times greater. The two authors have introduced a colour scheme to present them: A vivid green stands for the validly published and “currently accepted” names of genera. Light green is the colour of the validly published but “not currently accepted” tax0ns – among them are e.g. Listera (now: Neottia) or Aceras (now Orchis). The deprecation is explained with molecular-genetic studies: “Current DNA testing of this genus shows that Aceras is clearly nested within Orchis.” With the same reason Nigritella is put to Gymnadenia – but Barlia is printed in vivid green as an accepted taxon, though Barlia robertiana was classified as belonging to Himantoglossum  by molecular biologists.

The compendium explains classification and etymology for each genus listed, followed by a synopsis of the genus with the number of species, geographic distribution, favoured habitat and a short description of morphological features. For each genus there is an illustration of a flower. In the global context the European genera of orchids appear in a a rather limited scope. The authors state that they expect the discovery of new species but these may find their place in the now existing structure of genera.

Weiß blühende Orchideen mit einer anderen Standardfarbe werden oft als “Albino”-Form bezeichnet. Tatsächlich aber können Albino-Pflanzen, denen das für die Photosynthese unerlässliche grüne Pigment Chlorophyll fehlt, durchaus farbige Blüten haben, wie diese Aufnahme einer Cephalanthera rubra aus Thüringen von Holger Disse zeigt.

Umgekehrt haben die meisten Albiflora-Orchideen zwar weiße Blüten, aber durchaus kräftig grüne Blätter und auch einen solchen Stängel. Ihnen fehlen die für die Blütenfarbe relevanten Pigmente aus den Gruppen der Carotenoide und Anthocyanine. Sie verfügen aber über reichlich Chlorophyll, erhalten also auch Nährstoffe aus der Photosynthese.

Bei manchen Orchideen ist die Ausbildung der Blütenfarbstoffe reduziert, Anthocyanine werden aber noch in geringem Ausmaß gebildet, wie es bei der hier gezeigten Cephalanthera rubra der Fall ist. Diese weiß blühenden Pflanzen mit einem Hauch von Standardfarbe könnten als Teil-Albiflora-Form bezeichnet werden.