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Thread: How does one tell them apart?

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    Cardiac Nurse JB_OrchidGuy's Avatar
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    Ok I was just looking up some pictures of the few dews I have. How does one tell the different dews apart? I am talking about like D. tokaiensis from d. intermedia to d. capillaris. They all look the same basicly. Is it because of the flowers? Basicly like how the majority of Cattleya orchids look the same, but the flowers are different?
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    Hi JB_,

    That sir is a very good question, LOL. There isn't an easy answer. Experience plays a big role in observational taxonomy. The more individuals you are exposed to, the better your eye gets. Various sections within Droseracae have their own criteria. Probably the most significant feature is generally (but not always) the floral details of the peduncle and where the scape arises, details of the sepals in regards to absence or presence of hairs, nature of the hairs on the scape and stipule division. The division of the styles is very important as well in many species. Details of the lamina as regards to shape: truncate, spatulate, round. Details of the seed testa sre also diagnostic. Least reliable are size and color since these change relative to the growing conditions.

    In the cases you site, the upright held oval lamina held on petioles devoid of hairs, typical white flower and formation of hibernacula reveal this species. The hybrid D. tokaiensis is very similar to D. spatulata but with rounded lamina. For D. capillaris the details of the divided stipules is a good indicator.

    No, they don't all look alike I can assure you. After awhile it isn't all that difficult to place the various species. I still have problems with some of the less familiar species like the pygmy Drosera and the South African species present a sticky problem (hehheh) due to the unrestricted fertilization in contiguous populations and complex hybrids possible with members sharing the same karyotype.

    The various species in world wide distribution have certain characteristics that let you place them geographically for example looking at D. slackii, aliciae, admirabilis, cuneifolia there is a particular width of the petiole and lamina, and they are truncate to more or less of a degree. Seeing this, one places them as South Africans and we go from there probably using Obermeyer's Key to the South African Drosera Species

    The Brasillian forms have a hariness and often deep red color.

    Seed pods of the D. spatulata complex have reflexed sepals that do not close all the way, presenting a star like appearence when the seed is ripe a feature unique to this complex.

    Of late cytological studies have been used to trace gene markers and seems to be regarded as the final word on species rank. It is not. Phenotype is not the function of a single gene, but the interplay of the entire genome, but it is another window into a 20 million year old process, and we welcome the data.

    Other plants are easy to key: hard to mistake a Petiolaris Complex member, or D. regia!

    Oh, it's not often cut and dry. Taxonomy is a highly opinionated science. Always remember the holotype is one member out of millions and can never capture the variation present in the field, asnd here again it is only the degree of the authors experience that lends credibility to the concept. It would be nice if we looked up a particular individual in the appropriate keys to find it conforms exactly, but this is more the exception rhan the rule.

    I feel "species" is a verb and not a noun. In the end it is "best guess" whether done by the botanist in the field or the horticulturalist. Herbarium studies are essential, familiarity with the literature and experience cultivating many different individuals, and ideally field work all contribute to a sort of gestalt impression. Least useful is photographic consensus. A look at Bob Z's site will reveal the problems there: if I have a plant I think is D. ascendens (but actually is D. spatulata) and I go to Bob's site to confirm it. Once there if another grower has made the same error (these mistakes get handed down and passed on and on in a legacy of confusion) and posts *his* equally incorrect photo of D. ascendens and it looks *just* like mine, then I accept the error and pass it on along with the seed. This is especially true for the less common species. This has happened to me more than once.

    Add to the mud stew the possibility of cross fertilization within collections and things get really complex. I sent out D. dielsiana seed, and when the recipients showed me what grew from the seed I distributed I was aghast to find it was nothing like the parent plant, and I did not make any mistakes when I harvested it! Obviously there has been unexpected fertilization and the result was a hybrid. I can always tell a hybrid from the depth of the marks in the brick wall where I bang my head.
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    Cardiac Nurse JB_OrchidGuy's Avatar
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    Thank you very much Tamlin. That was a good explination. I realize they all do not look alike, but the three I mentioned, D. tokaiensis, d. intermedia and d. capillaris all look alike to me except for variation of color. I know the Adelea looks different and as well as others. I was just curious as to how to tell the ones that look similar apart like the three I mentioned. Your explination was great. I stumbled a little on some of the terminology, but got the gist of it.
    Thanks for letting me know that D. Tokaiensis is a hybrid. I know when an orchid is listed as a hybrid it either with the two parents name or part after the genus is capitalized. When I got Tokaiensis it wasn't capitolized so I thought it was a species. And the more I look at it the more I think it looks like cappilaris and intermedia except intermedia is not as red as the other two in my GH. So the flower plays a role in IDing the plant. That is understandable.

    I am still not sure what a peduncle, stipules, and hibernacula are.

    I guess I just need more experience with them. I remember when I was first getting into orchids it was a little confusing too. Thanks again.
    JB
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    Well it's time for a terminology lesson then.

    Hibernacula are winter resting buds made by temperate Drosera species like D. rotundifolia and D. intermedia.

    Peduncle is the flower scape including the flower buds and the small modified leaves that surround them known as "sepals"

    Sepals have specific shapes too, hairs, and the presence or absence of glands - all important considerations.

    Stipules are the white hairs rising out of the center of the plant. They can be either adnate (connected) to the petiole or free from it. They may be fused or variaby divided at the ends.

    The petiole is the long part of the leaf that has no traps on it. It may be hirsute (hairy) or glaborous (smooth). The cross section of the petiole is also good. The petiole blends into the lamina (the trap bearing portion of the leaf, and the degree of tapering, number of hairs, and association with the stipules (as above) are important.

    The lamina as mentioned are the trap bearing portion of the leaf. The shape (oviod, round, truncate, spatulate) and the placement and orientation of the motile hairs, and the shape of the glands at the end of them are diagnostic. The presence or absence of hairs on the underside of the lamina are also considered.

    LOL, to me seeing D. intermedia and D. spatulata x D. rotundifolia (= D. tokaiensis either form of nomenclature is correct) is like looking at a caucasian and an Oriental! No doubt you have orchids that would look identical to me and you'd think I was blind, hahaha!

    I have been fortunate to have been helped by some very good taxonomists and field workers who took the time to send me the publications I needed for my study of this genus. Dr. Robert Gibson (well, almost there), Dr. Schlauer, Phill Mann have all been very generous. These papers are often hard to procure, and sometimes in other languages. I will be happy to fill any specific requests for literature as regards this genus if I have it. I find the line drawings in the Keys to be better than photo's since they focus keenly on the essentials.

    Thank you for your interest in Drosera systamatics, a subject formerly near and dear to me. These days, I couldn't care less as to what they are named. I care only for their beauty as individuals and still find them the most beautiful of all CP's.
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    BTW: D. tokaiensis *is* a species, although a recently evolved one. There was a very good discussion of the subject on the CP Listserve from back in the 80's or early 90's. Search the archive and read all about the debate....it was quite interesting.
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    Cardiac Nurse JB_OrchidGuy's Avatar
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    Ok Tamlin tell me about this list server. I don't know about it. I find it interesting on how the taxonomists destinguis different plants apart. Even with the orchids, but no one was ever really interested in explaining to me how they came about distinguishing some species. I always thought the flower, but then someone said morphology, but then never explained. So this is very interesting and THANK YOU so much for explaining it to me. After I get done with my nursing school I plan on taking some botiny so I can learn taxonomy a little better.

    Also Tamlin. Can you give me a list of the BIG dews? Or should I just give the ones I have time since they were started from seed. My capillaris are flowering so I assume they are about full grown. They are a little bigger than a quarter. Thanks again!
    JB
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    Cardiac Nurse JB_OrchidGuy's Avatar
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    Oh Tamlin I really need to read the debate on the D. tokaiensis. Before asking these questions, but I am going to ask anyways. Was it a natural hybrid? I am still not certain on what makes a species a species since everything evolved from one individual plant. Like all dogs evolved from the first two dogs.

    I know that a species has two sets of alleles and they are both the same in a species, but when you start hybridizing the alleles no longer are the same since you get one allele from one parent and the other allele from the other parent, and if they are different species then they're are two different alleles resulting in the different plant. Maybe I am not using the proper terminology. I just got out of bio 2 and I will be damed that after a couple of months not using it, I forgot a lot of it.
    JB
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    Quote Originally Posted by [b
    Quote[/b] (JB_OrchidGuy @ June 19 2006,4:34)]I am still not sure what a peduncle, stipules, and hibernacula are.
    There are a few botanical dictionaries on the web that can be very helpful when you run across terms you have not seen.

    Here's one Although it seems quite slow...
    All the best,
    Ron
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