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Drosera Section Arachnopus Under the Microscope
Hartmeyer, S. (2004)  Carniflora Australis (AUSCPS) Number 3: 11-17  (Deutscher Text: "Neues vom Sonnentau")

The Indian Sundew (Drosera indica) occurs with a huge extension, from South Africa over Madagascar up to India and through Southeast Asia down to Australia. The plant colour reaches from yellowish-green to dark red, the flowers are white, orange or pink - or start white and become pink after some days - and the size varies from only a few centimetres (i.e.: Howard Springs, Australia) up to respectable more than 150 cm (i.e.: South Africa). They all grow in tropical or subtropical environments. Despite of several obviously distinct varieties, until December 2000 they all have been classified as one species into the monotypic (since the three North Queensland Sundews have been separated into section Prolifera) Drosera section Arachnopus. Then Dr. Jan Schlauer described the Australian D. hartmeyerorum, and classified it as a second species on its own into section Arachnopus. Closely related to D. indica, this dark red plant from the Eastern Kimberley is clearly distinguished by light yellow emergences of approx. tentacle size at the leaf base, which are even unique for the whole genus. Their purpose or function is still puzzling and object of further investigation (News on this topic in our Artikel Drosera hartmeyerorum - Der Sonnentau mit Lichtreflektoren  Hartmeyer, I. & Hartmeyer, S. (2006)  DAS TAUBLATT (GFP) 2006/3: 4-9). But there is one more surprise: the microscope shows very minute and distinct structures spread over the leaves of different varieties of D. indica.

At the 4th International Carnivorous Plant Conference in Tokyo (Japan 2002) I have been invited by Prof. Kondo to show parts of our video "FLEISCHIMANIA", on which the yellow (magnified) emergences of D. hartmeyerorum are visible (including plants and habitat). This species found a lot of interest and I was very pleased, when after the lecture Prof. Dr. Stephen Williams (Lebanon Valley College, USA) offered a common project (together with Prof. Al Wolf and Dr. Regina Kettering) to investigate the species with a Scanning Electron Microscope (SEM). Well, to realise such a project would normally be very expensive. so i agreed without hesitation. The chemicals to prepare some Sundew leaves - grown from seed at our greenhouse in Weil am Rhein, Germany - arrived soon from Pennsylvania, USA, and only a few days later I returned the specimen for the SEM investigation. This is still ongoing, however, I am very grateful for the approval of Stephen and his team, to show the excellent two SEM-pictures (figures 1 and 2), to accompany this article.
REM D. hartmeyerorum 1 REM D. hartmeyerorum 2
SEM-pictures of Drosera hartmeyerorum SCHLAUER by Dr. Regina Kettering. Published with the kind approval of Prof. Dr. Stephen Williams and his team at the Lebanon Valley College, USA.
The collapsed cell on one emergence shows, that the "lenses" are hollow. The normal tentacles beside allow to match the size.
D.hartmeyerorum Photo B. Rice 2 D. hartmeyerorum Photo B. Rice 1
Drosera hartmeyerorum SCHLAUER photographed by Dr. Barry A. Rice ( with a special lens combination.
A good comparison between the yellow emergences and the deep red leaves.
The description of the yellow emergences caused a discussion on the Internet and motivated several persons world wide to take a closer look through the microscope. Thus I was again very pleased, when I received some excellent colour photos (Figure 3 & 4) by Dr. Barry A. Rice (editor of "Carnivorous Plant Newsletter", ICPS) who did not use a microscope, but a special combination of photo-lenses to achieve the great magnification. Again I am very grateful for Barry's approval to show them to accompany this article. Together with the SEM pictures a good general impression of the unique yellow emergences becomes possible.

The story was getting even more exciting when Dr. Eberhard König (Germany) told me, that the big green D. indica that he has on his list, shows very minute mushroom-like structures on the whole lamina. Visible only under a microscope with 200 times magnification. I recalled a comment by Stephen Williams (private communication), that apparently the "head" of the yellow emergences of D. hartmeyerorum is built by only a few giant cells (one "lens" = one single cell). Could it be possible that varieties of D. indica can be distinguished by those very small structures which have not been found until now, because of their minuteness?

At a meeting of the German CPS "GFP" in Wuerzburg (German town) 2002, I met Andreas Fleischmann who has an excellent knowledge on the Droseraceae. He also found different very minute emergences on his D. indica and offered some seeds of such varieties. They germinated well and thanks to a weekly feeding with fish-food (using tweezers with a magnifier) they grew quickly. For closer observations I decided to buy a USB-microscope (Internet order approx. US$ 250,-), which is connected directly to the computer (by USB port) enabling 30 and 200 times magnification. A light source is integrated and combined with a laptop the microscope can be used even in the field on living plants. Unfortunately the resolution of the resulting pictures is just poor, but good enough to get more information. A high quality microscope with camera adapter would be 10-20 times more expensive!

When the plants had grown big enough to investigate the adult leaves, I needed 200 x magnification and could then clearly confirm the observations of Eberhard Koenig and Andreas Fleischmann. As mentioned above: the resolution of the resulting pictures is only poor for printing, but I believe they are interesting enough to show them.
D. indica Emergenzen

D. indica Emergenzen

D. hartmeyerorum seeds
Drosera aff. indica "white flower" (200 x mag. - USB mic.) - growing in South Africa - small mushroom-like yellow emergences appear. Seeds of D. hartmeyerorum
200 x mag.

D. indica SA Emergenzen

On this Drosera serpens (200x mag. - USB mic.) - growing in the Eastern Kimberley - the whole lamina shows several only 0.1 - 0.2 mm small emergences with yellow heads.

(Left photo)

This former D. indica "pink flower" from the Eastern Kimberley (AUS) has been renamed in 2014 into 
Drosera serpens.

(Names corrected here in January 2016)

D.- indica seed

Seed of D. serpens
200x mag.

Due to the huge extension of D. indica it will be a long lasting and hard work for everybody who tries to publish an extensive and complete documentation of all varieties (or new species?) of this Sundew. To investigate the very minute emergences on the world-wide existing dried herbaria specimen will certainly be not so easy. And in addition there is still a bigger problem: no matter if anybody is looking on the minute emergences, genome or seed structures of the species, actually, at this time much more field observations will still be necessary because several unexplored growing sites between the African and the Australian eastcoast are still waiting with unexpected surprises.
The intention of this article was not to deal with any new species names, but to motivate CP enthusiasts to focus on the minute emergences on D. indica varieties at their own collection. There are more different emergences than the shown examples! Godd luck! It would be great to hear from you by email.

Hartmeyer, S. (2003), Neues vom Sonnentau: Die Sektion Arachnopus unter dem Mikroskop. DAS TAUBLATT 2003/3:04-08.
Schlauer, J. (2001), Drosera hartmeyerorum spec. nov. (Droseraceae), a New Sundew in Sect. Arachnopus from North Australia.

Hartmeyer, I. & Hartmeyer, S. (2001), Observations on a New Drosera species in the Ord River Region (Australia). CARNIVOROUS PLANT NEWSLETTER 30/4: 107-110.
Hartmeyer, I. & Hartmeyer, S. (2001), FLEISCHIMANIA, Hunting Veggies® Digital Video, 60 minutes (German and English language), private production.

Hartmeyer, I. & Hartmeyer, S. (2002), THE 4th INTERNATIONAL CARNIVOROUS PLANT CONFERENCE IN TOKYO, Hunting Veggies® Digital Video,
170 minutes (English language), private production.