Porroglossum dalstroemii

Porroglossum dalstroemii is endemic to mossy cloud forest of southern Ecuador (Province of Morona-Santiago), altitude around 1800m (Luer 1987).  It is a cute minituare species with its leaf about 4-5cm long.  The flowers are small and not showy, but the sepals are all fused together and the shape is interesting.  I received my plant in December 2014 from Andy's Orchids, and it seems to be almost always in bloom.  It is an easy grower under my condition.  I'm growing it at the cool-end of intermediate; max/min daily temperature of 29/18C (84/65F) in the summer and 21/13C (70/55F) in the winter.  It seems to be ok in a fairly shady condition (PPFD of 55 µmol m^-2 s^-1)..

The flowers are upside-down compared to a typical orchid species, and the lip is located at the top side and the dorsal sepal is at the bottom.  This is called non-resupinate flowers (link to Wikipedia about resupination). It is interesting that you can see that the ovaries are twisted to have non-resupination.  As you can see in the photo of the plant, the orientation of the flowers is not always consistent, but the majority of the flowers orient in the non-resupinate direction.

Note the twisted ovary (the green part right side of the flower) to achieve non-resupination.

One of the fascinating characteristics of genus Porroglossum is the actively moving lip.  The genus name is derived from Greek; porro (I think it means "forward") and glossum (tongue=lip).  You notice that the lip is fairly far away (forward?) from the column.  In general, the lips of orchids are reproductively important since they help to guide the pollinators for the precise deposition and reception of pollinia.  So one may wonder the lip located so far away from the column many not be a good design for precise pollination.  But they have a better trick to increase the pollination efficiency.  Once an insect lands on the flower and wiggles around, the lip snaps close, trapping the poor insect.  See the video below. After a while, the lip opens and pollinators are free to go.  This movement is probably initiated by touching or vibration of insects.  It is somehow similar to the Venus flytrap (Dionaea muscipula, a carnivorous plant) capturing its prey, and it is an example of thigmonastic movement.  With the Venus flytrap, the trap has sensing hairs which sense the movement of insects.  However, the actual mechanism of the movement of Porroglossum lips doesn't seem to be known yet.

It is also amazing that this type of actively moving lips has evolved multiple times within Pleurothallidinae (Pridgeon and Chase 2001, Merino et al. 2009).  This type of lips are observed in former genus Acostaea (currently Specklinia), two species of former Condylago (Stellis rodrigoi and S. furculifera (Dresseler and Boagarín 2007)), Masdevallia teaguei, and some Trichosalpinx (e.g. T. blaisdellii).

The lips are triggered and closed.

Below, I'm showing the details of the flowers. Parts of the flower were removed to show the features.

lip, which acts as a trap door.

Sepals are removed to show the lip in the open position, and the small petals along the column. The twisted ovary is obvious in this photo.  Note that I'm showing it in the opposite orientation (the lip is at the bottom). 

Petal.  The other petal behind the column is removed.

Column.  The petal and motile lip are removed.  The petal behind the column is still attached.

Column from the top side (dorsal sepal side).

Column from the bottom side (lip side), showing the stigma.

You can compare the details against the original illustration below.

Illustration from the original description (Luer 1987)
© Missouri Botanical Garden. 1987. Porroglossum dalstroemii Luer. Swiss Orchid Foundation at the Herbarium Jany Renz. Botanical Institute, University of Basel, Switzerland.

Literature Cited:

• Dressler, R. L., & Bogarín, D. 2007. A new and bizarre species in the genus Condylago (Orchidaceae: Pleurothallidinae) from Panama. Harvard papers in botany, 12(1), 1-6.
• Luer, C. A. 1987. Icones Pleurothallidinarum IV. Systematics of Acostaea, Condylago, and Porroglossum (Orchidaceae).  Missouri Botanical Garden Press, St. Louis, MO, USA, p. 44-45.
• Merino, G., Doucette, A., & Pupulin, F. 2009. New species of Porroglossum (Orchidaceae: pleurothallidinae) from Ecuador. Lankesteriana International Journal on Orchidology, 9(3):459-466 (full PDF can be downloaded from this link of ResearchGate) 
• Pridgeon, A. M. and Chase, W. M. 2001. A phylogenetic reclassification of Pleurothallidinae (Orchidaceae). Lindleyana 16: 235–271.