What's new
TerraForums Venus Flytrap, Nepenthes, Drosera and more talk

Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

What Exactly is D. sp. South Africa?

  • #21
DSC_00110001_3.jpg

DSC_00140001_2.jpg

DSC_00130001_5.jpg
 
  • #22
Mach

You could always try typing it out from the description. There's not enough detail of the stipules in the photos. Note it is mentioned that the flowers rarely open in cultivation.

http://www.omnisterra.com/botany/cp/pictures/drosera/0075.htm#D.dielsiana
5. Drosera dielsiana

5. Drosera dielsiana Exell & Laundon in Bol. Soc. Brot. 30 : 214 (1956). Type : Transvaal, Lydenburg district, near Spitskop, Wilms 35 (BM, holo.).

Small, hairy herbs with compact, basal rosettes and a few fairly long thin roots. Leaves 15-25, the old leaves soon disintegrating, apetiolate; stipules small, fimbriate, auriculate; lamina spathulate, up to 2 cm. long, 6 mm. broad above, apex rounded, tapered below into a broad, hairy petiolar part; both types of tentacles present; lower surface sparsely hairy. Inflorescence with the scape leafless, sturdy, straight or rarely somewhat curved below, 10-20 cm. long, hairy near the base; usually about 8-flowered (3-12) with the rhachis erect; flowers secund, small, seldom open according to collectors; pedicels 2 mm. Calyx-lobes c. 5 mm. long. Petals obovate, unguiculate, c. 7 mm. long, pink, mauve, violet or white. Stamens with narrowly winged filaments. Styles forked from the base with the stigmatic apex spoon-shaped, membranous. Capsule oblong, 5 mm.; seeds ovoid, 0.4 mm. black, honeycombed. Fig. 28:5

Found on the escarpment in the eastern Transvaal, in Swaziland and northern Natal and further northwards in southern tropical Africa, apparently on mountain plateaux. Flowering during the summer months.

NATAL.-Utrecht : Naauwhoek near Utrecht, Devenish 978.

SWAZILAND.-Mbabane : Nduma, Compton 25381

TRANSVAAL.-Barberton : Godwan River, Berlin, Hofmeyer sub PRE 15280. Letaba : The Downs, Junod 4427. Lydenberg : Steenkampsberg, 15 kilometres E. of Draaikraal, Strey 3031; Mount Anderson, Strey 3536; Galpin 13738; Prosser 1796. Pilgrim's Rest : Mariepskop, Van der Schijf 4544; Meeuse 9954.

Since the flowers seldom open, it is possibly an apmoict.
 
  • #23
I knew that was online somewhere. kept on forgetting. Will be trying to do the microscopic photos of the seeds next week.
 
  • #24
Christian,

I think you are an "expert" on these South African taxa and have learned much from you! Besides, you've been there!

I've written to Robert regarding this strange and confusing plant and am awaiting reply.

NAN, part of the problem with diagnosis is that when using the published Keys all of the criteria must be examined and taken into account. Often, there are some criteria present that support a diagnosis, but rarely are all the criteria present in any given example, and my teachers have stressed there is no better or stronger indicator, all criteria have equal value. When studying herbarium sheets or doing field work, the difficulty is not so great because there are numerous examples from which to compare, but for "orphaned" plants in collections there is usually just the example presented and "pure" species meeting all the conditions for diagnosis simply don't exist in individuals. Even the "type" specimens are subject to this variability. Taxonomy is a highly opinionated science, and opinions are only good as familiarity allows. Christian has grown and studied these taxa more deeply than I have I believe so I respect his opinions more than my own impressions.

I agree, there isn't much sense in discussing origins except for the mental exercise (or head banging if you prefer). The best solution for future generations is to publish it at cultivar rank, providing some history and a central reference for horticultural growers interest vs taxonomists. I would be pleased to do so if I ever have a chance to grow and assess it. It needs doing!

Hopefully, Dr. Gibson will shed some light on the mystery, I respect his opinion most of all!
 
  • #25
Hi,

this is looks like the plants again, that i do not think are D. dielsiana at all! Btw, the description above from Obermeyer is not the type description! But it is good enough to show you, that the plant above does not fit ;)

"Inflorescence with the scape leafless, sturdy, straight or rarely somewhat curved below"
I can easily see a very much curved scape!

"Styles forked from the base with the stigmatic apex spoon-shaped"
The stigmatic are divided not only at the base, but also towards the apex. So, this should also not fit!

I am really looking forward to the seed pictures! I would not be surprised if they would not fit: "seeds ovoid, 0.4 mm. black,"

So far my understanding, others might have different opionos ;) Btw, i really like discussing these plants!! Thanks for asking Dr. Gibson, William! I am really intersted in his opinion!

regards,
Christian
 
  • #27
Hi,

thanks! That's not ovoid to me! So, i still think i am right and almost noone is cultivating true Drosera dielsiana.

Christian
 
  • #28
without magnification they looked superficially round. Even at 10X hand lens inspection. Seems my eyes are going bad faster than I though. Put them under a scope and details start emerging.

Have had one idea that is bugging me. can see cultivation conditions affecting things like color and leaf size and or shape in some cases. It probably wound never affect seed morphology (perhaps size at the most) so couldn't the shape and external morphology of the seeds be used almost like fingerprints? Admittedly might need to do SEM work to see the ridges and intricate details as I was pushing my scope and doubt I have the quality to do that much detail........
MTF
 
  • #29
I have Dr. Gibson's response regarding Drosera dielsiana. As I anticipated, he referred me back to the publication by Excel and Launders and shares my opinion that the "best" criteria is the seed form and texture taken into account with the division of the styles.

"You have raised an interesting question about Drosera dielsiana/ D. natalensis. Drosera natalensis is a highly variable taxon and I am not sure if I have seen its typical form (but have finally received seed of the apparently 'true' D. natalensis that I look forward to flowering over the coming summer). What I thought may have been D. natalensis in the field, on the South African south coast between George and Tsitsikama now appears to be D. aliciae - all of my samples were sent to Germany and I have so far not had a chance to study any material in more detail. I am reasonably confident that I saw D. dielsiana in the wild between Knysna and Durban, based primarily on leaf shape. However, as shown in the Exell and Laundon paper in which Drosera dielsiana was described the key difference between D. dielsiana and D. natalensis is seed size (and also style division) and between D. natalensis and D. aliciae is the nebulous character of leaf 'toughness'. The problem is also compounded by natural and artificial hybrids between D. natalensis, D. venusta (if indeed this is distinct from D. natalensis), D. dielsiana and D. nidiformis."

I include this quote for the range data it contains, in hopes it may prove useful on your next visit to South Africa:

"The chromosome counts would not suggest it is a recent hybrid, but other genetic work may shed some useful insights into its origins. Its current distribution is sporadic; along mountain
tops from Natal to Zimbabwe".




Unfortunately, neither of these characteristics are 100 percent dependable. Seeds from cultivated plants are typically longer, and there is always the question of random hybridization. Simple variability ( even in the field populations) means that taxonomy must be a best guess, taking into account all the criteria. As Robert cautions:

"Seed and flower structure would help, but beware the absolutes in publication for these plants do not read them and merrily disregard them, e.g. Excel and Laundon's paper. As to to what the "true" species looks like this has been set by the designation of the type species. Hopefully what was collected and designated such was typical of what was there - but there are no guarantees. Also, many early collections have been made in the absence of a good knowledge of full variation within the species (e.g. within the D. peltata complex), and in the intervening time many populations have been wiped out. Thus it is all good arm-waving stuff, and an article on it would surely generate some interest, and show how much subjectivity there is in taxonomy."

This brings me back to my assertion that purity in tfrica is optimistic in the extreme for this genus even for field researchers with long experience with these populations and likely totally impossible for horticulturalists dealing with orphaned plants.

I believe that if the seed is small and ovoid, and if the styles are MOSTLY of simple bifurcation, a reasonable determination could be for Drosera dielsiana.

---------- Post added at 05:00 AM ---------- Previous post was at 04:48 AM ----------

Aloha kulamauiman!

As mentioned above seeds are indeed affected by etiolation in cultivation, and even seasonally (winter vs summer) when taken from habitat.
There are no absolutes.
 
  • #30
Hi,

thanks for the post, William!

i don't doubt that seed shape and division of the styles are most likely the best way to differentiate between Drosera natalensis and Drosera dielsiana! Having said this, the flowers and the seeds in all plants i have so far seen identified as D. dielsiana do not look at all like what i would imagine from that species. I also can in no way imagine, that the seeds of the above shown plants would be ovoid if this plant grew in habitat. The seeds of the picture are clearly fusiform (according to my understanding). These caracters both put the plants to D. natalensis for me.

William, did you show Dr. Gibson the pictures of the plants here? I would really like to know what he says to these plants. Could you get me in contact with him, Tamlin?

regards,
Christian
 
  • #31
Hi Christian,

Robert did not comment on the question of D. ????. although I do believe he is aware of this plant. I will write to him with an introduction to you, and will inquire if he wishes the correspondence. He is a very kind (but busy) gentleman and if he is willing I will send you his email addy.

You are correct, the seeds are fusiform and do not support the determination for Drosera dielsiana based on this criteria.

I have an off topic question for you. Have you ever seen any Drosera natalensis from Madagascar?
Dr. Schlauer told me once in a correspondence that this locale is likely to have the most "pure" D. natalensis, but I have never seen these plants and would very much like to!
 
  • #32
Hi,

thanks!

So far i have not yet grown or seen D. natalensis from Madagascar. The type of D. madagascar is from the Area around Durban, so i really wonder why the plants in Madagascar should be the most pure ones. I will have to ask some of our german experts about this plants in the near future. This topic has really increased even more my interest in these species!!

Christian
 
  • #33
Yes, it has me going through all the old papers too. I came across some good botanical drawings done by Robert on Drosera dielsiana and note that in his drawings the petioles are significantly more narrow than in most photo examples listed under this binomial.

Thanks a lot for the good discussion! Not too many folk are interested in taxonomy matters.

I've gotten back in contact with some of my former research associates. You might recall I was working with the Idaho State Herbarium who were producing some awesome digital seed photos. My associate is no longer with this herbarium but is well connected with other agencies that might want to continue the work. I was able to use my world wide contacts back then to acquire good native Drosera seed from Australia with good success, and somewhat with the Brazillian endemics too. I would like to continue with the project and begin sourcing native South African seed just in case you might be interested in donating any such material to a good cause.

I've been accused in the past of using the project to "steal" seed for my own collection, but that wasn't the case back then or now. I'm waiting to hear from other agencies before going to work, but keep me in mind for a few seeds if you get a chance to collect. I'm hoping the new agencies may be more active in producing the photo's, that was a problem last time. My associate still has seed from what a sent a decade ago, it's just hard to find anyone willing to do this labor for love.

My growing days are over, but with my renewed energy I want to do something good while I still can
 
  • #34
I've been accused in the past of using the project to "steal" seed for my own collection, but that wasn't the case back then or now.

One of the former managers of the ICPS seedbank was more or less accused of the same misdeed. What petty creatures we humans can be. But then again Neitzsche did say "It is only the lower intestine that keeps Man from thinking he is God."
 
  • #35
I always liked the quote, "You have enemies? Good! That means you stood up for something"
 
  • #36
Mach, those look like the seed that I recently received as D. dielsiana. The seeds are definitely fusiform with elongated testa on both ends.

No joy.

Ian - take note.
 
  • #37
yep. this one is wide spread. i got from the seed bank. And sent back to the seed bank. OTOH I have some that are nataensis growing up should be able to get pics of seeds etc for comparisons. more and more I am beginning to think we need a means to fingerprint these guys and seeds seem the logical way to do it.

MTF
 
  • #38
Jost some comments here on the idea of seed fingerprints. It was the focus of my research almost a decade ago now. I thought, then, how hard could it be to produce a good reference of seed details, with the power of the internet allowing easy visual exchange of good digital photo's.
Well, it isn't that simple. I leearned that the whole comcept of "type" is completely optimistic. It's always a best guess, closest fit sort of thing with observational taxonomy, simply because "species" is not a noun, it's a verb. In other words, individuals do not comform in nature to the type, because they express so much variability, both from their genitic makeup and also from regional and seasonal effects.

In regards to seed, it too must be a best guess. Location data, and season of collection will affect how it compares to the "type". I once thought that from habitat, the seed would demonstrate a "fingerprint" that couldn't be mistaken. Conversations with other taxonomists involved in field and herbarium studies taught me that even this much is not dependable for the reasons stated above.
Seed from private cultivation is totally unreliable.

So we guess. How many of the other characteristics are present in the subject example to support or deny a determination? At the same time, please remember that taxonomic review and even publication at species level deals with ego issues. If the publisher and the reviewer are friends, all is peachy keen for Species Novae publication and acceptance. If they are not. the publisher gets the short (misspelled intentionally) end of the stick. Yes, you can bet it happened in the past, and it happens today as well. Maybe one reviewer didn't know anything at all about the subject in question, liked the author and granted legitimacy to a totally useless example for future consideration as the "type".

Such are the plagues that are part of observational taxonomy. They are a natural consequence of the impossibility of trying to categorize and establish limitations on an ongoing evolutionary process, and also a consequence of valuing over highly ones personal opinion over anthers based on the letter's of a Degree that may or may not mean anything at all.

The best WE can hope for is to study the published material available, grow many examples and compare them to the published literature. We can visit the populations, see what other's are calling this or that, and then follow our heart's on it all. In the end, for everyone, after all the papers and whatnot you feel it in your gut, and you stand by that. For non-students....well, you find a guru and accept their more informed opinions, but they are just opinions. There are no ultimate answers.
 
Back
Top