Archivos de Diario para abril 2022

jueves, 14 de abril de 2022

Holothrix IDs in the Southern Cape based on leaves

@sedgesrock @malthinus @justinponder2505 @ren_hoekstra @christiaan_viljoen @milewski @knysna_wildflowers @tonyrebelo

We all know the frustration that comes from not being able to ID an orchid- especially when there is no flower. For when a flower is present, the Orchids of South Africa makes identification easy, but when the flower is absent there is not, as far as I am aware, a book concentrating specifically on orchid leaves. So this article aims to clear up some of the confusion regarding tricky IDs in the genus Holothrix- based on leaf structure, colour, hairiness, size and shape. All the type observations have leaf pics. I have included 11 species and 2 varieties as occuring in this area, namely:

Holothrix brevipetala- type observation https://www.inaturalist.org/observations/37464114
H. burchellii- type observation https://www.inaturalist.org/observations/97908227
H. cernua- type observation https://www.inaturalist.org/observations/99342981
H. exilis- type observation https://www.inaturalist.org/observations/98610067
H. grandiflora- type observation https://www.inaturalist.org/observations/10980768
H. mundii- type observation https://www.inaturalist.org/observations/92901849
H. parviflora- type observation https://www.inaturalist.org/observations/97642970
H. pilosa- type observation https://www.inaturalist.org/observations/95608185
H. schlechteriana- type observation https://www.inaturalist.org/observations/107177600
H. secunda- type observation https://www.inaturalist.org/observations/98290696
H. villosa var. villosa- type observation https://www.inaturalist.org/observations/99341754
H. villosa var. condensata- type observation https://www.inaturalist.org/observations/107879164

Firstly, we need to exclude some other species and families often confused with Holothrix.
According to https://www.inaturalist.org/taxa/119761-Holothrix, we are faced with the genera
Ornithogalum, Massonia, Satyrium, Eriospermum and Platanthera, an orchid genus from the Northern hemisphere.
I will exclude Platanthera from the start, assuming it does not and never will occur naturally in South Africa, let alone the Southern Cape.
In my experience, Eriospermum and Ornithogalum are the two genera that are most often confused with Holothrix.

Eriospermum examples can be seen here:
https://www.inaturalist.org/observations/77237656 Eriospermum dielsianum
https://www.inaturalist.org/observations/41748832 E. pubescens
https://www.inaturalist.org/observations/49986272 E. capense
https://www.inaturalist.org/observations/24740687 E. vermiforme
https://www.inaturalist.org/observations/11110583 E. brevipes

Observations where Holothrix and Eriospermum have been confused:
https://www.inaturalist.org/observations/95013397
https://www.inaturalist.org/observations/29227821

The two Ornithogalums most frequently confused with Holothrix are dubium and hispidum. See links below:
https://www.inaturalist.org/observations/75938927 Ornithogalum dubium
https://www.inaturalist.org/observations/77584041 O. dubium
https://www.inaturalist.org/observations/77870868 O. hispidum
https://www.inaturalist.org/observations/110642149 O. hispidum

Ornithogalum and Holothrix confusion:
https://www.inaturalist.org/observations/99701654
https://www.inaturalist.org/observations/51998115

Massonias are not generally confused with Holothrix, but confusion does arise at times. See below for typical Massonia examples:
https://www.inaturalist.org/observations/72673295 Massonia longipes
https://www.inaturalist.org/observations/89691522 M. depressa
https://www.inaturalist.org/observations/82992734 M. depressa
https://www.inaturalist.org/observations/82824040 M. setulosa

Examples of Holothrix- Massonia confusion:
https://www.inaturalist.org/observations/77043892
https://www.inaturalist.org/observations/32754037

The orchid genus Satyrium can normally be distigiushed from Holothrix by the large consistently glabrous light green leaves. These are typical examples:
https://www.inaturalist.org/observations/97142151 Satyrium membranaceum
https://www.inaturalist.org/observations/94206185 S. muticum
https://www.inaturalist.org/observations/102163407 S. acuminatum
https://www.inaturalist.org/observations/99341756 S. erectum

The inevitable confusion:
https://www.inaturalist.org/observations/87116912
https://www.inaturalist.org/observations/70733950
https://www.inaturalist.org/observations/85309674

One genus which Inat fails to list as a potential candidate for confusion with Holothrix is Bartholina. I include it here due to its close relationship with Holothrix and the fact that thay co-occur throughout this area. Bartholina differs from Holothrix in several ways with its small single leaf and prominent white veins in etheliae's case.
https://www.inaturalist.org/observations/94472308 Bartholina burmanniana
https://www.inaturalist.org/observations/101685854 B. burmanniana
https://www.inaturalist.org/observations/86025656 B. etheliae
https://www.inaturalist.org/observations/65139309 B. etheliae

Right- now that the other genera and families have been excluded we can get down to the nitty-gritty of Holothrix itself. I have made a simple key specially for this article- please note that the key is not completely foolproof and should not be used out of our area. What I mean when I say that the key is not watertight is simply that some populations of Holothrix cernua out of this region lack leaf hair.

Anyway, here it is. I'm afraid that I could not make a key for use with only leaves, and had to bring flower stalks and the flowers themselves into the picture, but I'll try to amend that with a list culled from Orchids of South Africa later on. I've also tried to make it as user-friendly as possible.

    1. Leaves hairy above....... 2.1
      -Leaves hairless above....... 3.1

  • 2.1 Leaves with "scales" or short hooked hairs....... Holothrix cernua
    -Hairs not hooked, lacking "scales" ....... 2.2

  • 2.2 Hairs on flower stalk deflexed - turned sharply downward....... H. brevipetala
    -Hairs on stalk more or less at right angles to the stalk....... 2.3

  • 2.3 Spur- little tail behind flower- less than or equal to 1.9mm long....... H. exilis
    -Spur greater than 1.9mm....... 2.4

  • 2.4 Lip 3-lobed ( divided in three ), central lobe curved upwards....... H. villosa var. condensata
    -Lip 3-lobed, central lobe no different from the others....... H. villosa var. villosa

  • 3.1 Underside of leaf hairy....... Holothrix pilosa
    -Lacking hair underneath....... 3.2

  • 3.2 Tiny hairs along leaf margin, spur straight....... H. mundii
    -Lacking marginal hair, spur slightly to strongly curved....... 3.3

  • 3.3 Bracts present....... 3.4
    -Bracts absent....... 3.6

  • 3.4 More than 7 bracts....... H. grandiflora
    -No. of bracts less than or equal to 7....... 3.5

  • 3.5 Relatively long deflexed hair on flower stalk....... H. burchellii
    -Hair on stalk, if present, pubescent ( like velvet )....... H. schlechteriana

  • 3.6 Lip 5-lobed ( divided in 5 ), lobes more or less rectangular....... H. parviflora
    -Lip 5-lobed, lobes linear, acuminate ( tapering to a point )....... H. secunda

In case there was any confusion or difficulty using the key, here are some useful tips and definitions:
What are bracts? See https://en.wikipedia.org/wiki/Bract and https://www.merriam-webster.com/dictionary/bract
And spurs? Those tiny "tails"? See https://en.wikipedia.org/wiki/Nectar_spur Also in https://www.inaturalist.org/observations/54393258 the spur is the tiny J-shaped curl visible on the lower 3 flowers.
When a leaf is referred to as being hairless above, what should it look like? See the third pic from the left in this observation: https://www.inaturalist.org/observations/31532859
And when a leaf is hairy above? https://www.inaturalist.org/observations/77229011 and https://www.inaturalist.org/observations/100227957 are prime examples of upper surface hairiness.
And what do hairy margins look like? ( article 3.2 ) See https://www.inaturalist.org/observations/92901849
And lip lobes? See the illustration of Orchis italica here: https://en.wikipedia.org/wiki/Labellum_(botany)

Info from the Orchids of South Africa and the Cape Orchids:
Holothrix breviptala- leaf pressed flat, hairy with stout hairs, less than or equal to 12mm in width
H. burchellii- leaf pressed flat against the ground, less than or equal to 60mm broad
H. cernua- leaf pressed flat, covered with short, stiff, hooked hairs above, less than 30mm broad
H. exilis- leaf pressed flat, sparsely hairy above, leaf width uncertain, probably 18mm wide
H. grandiflora- leaf pressed flat, glabrous, less than or equal to 80mm broad
H. mundii- leaf pressed flat, glabrous, short marginal hairs present, less than 21mm wide
H. parviflora- pressed flat or slightly raised, glabrous,less than or equal to 30mm wide
H. pilosa- leaves flat, upper surface glabrous, underside and margins hairy, less than 145mm wide
H. schlechteriana- leaf pressed flat to the ground, glabrous, less than or equal to 100mm wide
H. secunda- leaf pressed flat, glabrous, width uncertain, probably less than 80mm wide
H. villosa- both varieties- leaf pressed flat with a sparse to dense scattering of long hairs on upper surface, less than or equal to 95mm

Further reading:
http://redlist.sanbi.org/species.php?species=2841-2 Holothrix brevipetala
http://redlist.sanbi.org/species.php?species=2841-3 H. burchellii
http://redlist.sanbi.org/species.php?species=2841-4 H. cernua
http://redlist.sanbi.org/species.php?species=2841-9 H. exilis
http://redlist.sanbi.org/species.php?species=2841-12 H. grandiflora DDD
http://redlist.sanbi.org/species.php?species=2841-20 H. mundii
http://redlist.sanbi.org/species.php?species=2841-22 H. parviflora
http://redlist.sanbi.org/species.php?species=2841-24 H. pilosa NT
http://redlist.sanbi.org/species.php?species=2841-27 H. schlechteriana
http://redlist.sanbi.org/species.php?species=2841-29 H. secunda
http://redlist.sanbi.org/species.php?species=2841-32 H. villosa var. condensata
http://redlist.sanbi.org/species.php?species=2841-33 H. villosa var. villosa

Publicado el jueves, 14 de abril de 2022 a las 01:01 PM por ludwig_muller ludwig_muller | 8 comentarios | Deja un comentario

miércoles, 20 de abril de 2022

Epiphytic orchids in the Southern Cape: Identification by leaf

@milewski @jeremygilmore @justinponder2505 @christiaan_viljoen @malthinus @brendancole

By Ludwig Muller, SCHG (Southern Cape Herbarium, George)
ludwigxem@gmail.com

What are epiphytic orchids?
Epiphytic is best explained here: https://www.merriam-webster.com/dictionary/epiphyte
Basically, it's a plant growing on another plant without being parasitic. The host plant is normally larger than the epiphyte.
Most people, if they think of orchids at all, think of the epiphytic orchids. But here in the Southern Cape the majority of orchids are geophytes/terrestrial.
We are only supposed to have 9 species of epiphytic orchids here, but apparently Aerangis mystacidii has been reported from George and Knysna. Due to a paucity of recent records this species has been excluded, but can be seen here: https://www.inaturalist.org/observations/84737527 and https://www.inaturalist.org/observations/70134699 . Tridactyle bicaudata subsp. rupestris is not included in this article because it never grows on trees. The orchids listed here normally occur in dense Afrotemperate forest, and sometimes in coastal thicket.

The species list, with type specimens, is as follows:
Angraecum conchiferum- https://www.inaturalist.org/observations/99573537
A. pusillum- https://www.inaturalist.org/observations/10798465
A. sacciferum- https://www.inaturalist.org/observations/69713856
Cyrtorchis arcuata subsp. arcuata- https://www.inaturalist.org/observations/102243416
Calanthe sylvatica- https://www.inaturalist.org/observations/71129824
Liparis remota- https://www.inaturalist.org/observations/78057117
Mystacidium capense- https://www.inaturalist.org/observations/96900170
Polystachya ottoniana- https://www.inaturalist.org/observations/10859440
Tridactyle bicaudata subsp. bicaudata- https://www.inaturalist.org/observations/68215956
Note: Liparis remota and Calanthe sylvatica are normally terrestrial. However, you do find the odd specimen growing epiphytically, which is why they're included here.

Now that you know what the local orchids look like, we can deal with imposters.
Firstly, the fern Vittaria isoetifolia can be confused with Angraecum pusillum.
See https://www.inaturalist.org/observations/20291984 and compare with Angraecum observation above.

Next is Lepisorus schraderi, another epiphytic fern. It also grows as a lithophyte on occasion.
https://www.inaturalist.org/observations/68878068
https://www.inaturalist.org/observations/10822306
Compare with Mystacidium and young Cyrtorchis.

Pleopeltis macrocarpa could possibly be identified as an orchid.
https://www.inaturalist.org/observations/77108790

Elaphoglossum ferns are great candidates for confusion. See below:
https://www.inaturalist.org/observations/75070759
https://www.inaturalist.org/observations/103881674
https://www.inaturalist.org/observations/109748996

And finally the Paintbrush lily,Scadoxus puniceus. It sometimes grows as an epiphyte, notably the population on Hoekwil Big tree. See https://www.inaturalist.org/observations/107958850

  • Scadoxus is distinguished from epiphytic orchids by the purplish-black spots on the lower stem.
  • All epiphytic ferns can be distinguished from orchids by the lack of long, whitish roots clasping the host.

And now we can move on to identifying the orchids themselves.
As before, I have prepared a key. I think it's foolproof, but if you run into any hitches please let me know.

Leaves less than or equal to 8mm wide....... 1.1
Leaves greater than 8mm but less than or equal to 12mm in width....... 2.1
Leaves greater than 12mm wide....... 3.1

  • 1.1 Sympodial growth pattern/pseudobulbs present....... Polystachya ottoniana
    -Monopodial growth pattern/pseudobulbs absent....... 1.2

  • 1.2 Leaves at least 10 times longer than wide, grass- like, in a terminal cluster....... Angraecum pusillum
    -Leaves not grass- like....... 1.3

  • 1.3 Leaf margins not rolled / leaf V-shaped in cross section, stem to 350mm....... Tridactyle bicaudata
    -Leaf margins rolled ever so slightly, stems to 300mm....... 1.4

  • 1.4 Plant compact, stem less than or equal to 40mm, 4-8 leaves....... Angraecum sacciferum
    -Plant branching, stem less than or equal to 300mm, 8-16 leaves.......Angraecum conchiferum

  • 2.1 Leaf with prominent apical "V", stem less than or equal to 350mm....... Tridactyle bicaudata
    -Leaf lacking prominent "V", stem to 25mm....... Mystacidium capense

  • 3.1 Leaves pleated....... 3.2
    -Leaves bilobed....... 3.3

  • 3.2 Leaves less than or equal to 100mm long....... Liparis remota
    -Leaves greater than 190mm long....... Calanthe sylvatica

  • 3.3 Leaves with prominent apical "V", stem to 400mm....... Cyrtorchis arcuata
    -Leaves lacking prominent "V", stem to 25mm max....... Mystacidium capense

Terminology:
Sympodial growth- https://myfirstorchid.com/2016/07/04/monopodial-and-sympodial-orchids/
Leaf margins rolled- https://woodyplantstutorial.nres.illinois.edu/margins/mar-revolute.html
Apical "V"- a V-shaped indentation at the leaf tip
Pleated leaves- see first image at https://www.birdsoutsidemywindow.org/2018/06/16/pleated-leaves/
Bilobed leaves- https://www.collinsdictionary.com/dictionary/english/bilobate
Lithophytic- growing on rocks

If flowers are present identification will be a lot easier- I was going to make a flower key for this article but decided against it. If you need help with identifying an epiphytic orchid feel free to tag me @ludwig_muller
Note that it is possible, at least in theory, for the forest orchid Bonatea speciosa to grow epiphytically. I have never heard of this happening, but if you do find such a specimen it can be easily told apart from other epiphytic orchids by the prominent black "sheath" clasping the base of the stem. This "sheath" is shown clearly here- 2nd pic from left: https://www.inaturalist.org/observations/107758802
For more information, I would recommend Redlist. See below:
http://redlist.sanbi.org/species.php?species=2762-2 Angraecum conchiferum
http://redlist.sanbi.org/species.php?species=2762-4 A. pusillum
http://redlist.sanbi.org/species.php?species=2762-5 A. sacciferum
http://redlist.sanbi.org/species.php?species=2765-3 Calanthe sylvatica
http://redlist.sanbi.org/species.php?species=2815-1 Cyrtorchis arcuata
http://redlist.sanbi.org/species.php?species=2807-6 Liparis remota
http://redlist.sanbi.org/species.php?species=2790-4 Mystacidium capense
http://redlist.sanbi.org/species.php?species=2770-13 Polystachya ottoniana
http://redlist.sanbi.org/species.php?species=2821-1 Tridactyle bicaudata subsp. bicaudata

And finally, here is the info from Orchids of South Africa by Johnson & Bytebier:
Angraecum conchiferum- 8-16 leaves, adjacent, narrowly strap-shaped, unequally bilobed,
30-60 x 4-8mm, stem to 300mm. Often on Yellowwoods (Podocarpus sp, especially P. falcatus).
A. pusillum- 5-10 leaves, grass- like, linear, rounded, thin, in dense terminal cluster on stem,
40-160 x 3-4mm. Old inflorescences persistent.
A. sacciferum- 4-8 leaves, stiff, nearly erect, flat, linear to strap- shaped, obscurely and unevenly bilobed, 20-60 x 3-7mm. Stem to 40mm. Old inflorescences persistent.
Calanthe sylvatica- Leaves pleated, thin, 200-400 x 70-115mm, plant to 70cm.
Cyrtorchis arcuata- Leaves strap- shaped, folded together basally (Author's note: This trait is not very obvious or reliable), unequally bilobed, pale green, 100-160 x 20-30mm. Stem to 400mm.
Mystacidium capense- leaves strap- shaped, unequally bilobed, 40-120 x 10-22mm. Stem to 25mm.
Polystachya ottoniana- 2-3 leaves per pseudobulb/plant, linear to strap- shaped, 20-130 x 4-8mm. Up to 150mm tall.
Tridactyle bicaudata subsp. bicaudata- Leaves arranged in two opposite rows, leathery, linear to strap- shaped, rounded, unequally bilobed, 60-120 x 7-12mm.

Acknowledgements:
I wish to thank Dr Niels Jacobsen for his guidance and mentorship and Dr Brendan Cole for being so supportive of this project.

References:
Liltved, W., Johnson, S., 2012. The Cape Orchids: A Regional Monograph of the Orchids of
the Cape Floristic Region
. Sandstone Publications, Cape Town.
Johnson, S.D., Bytebier, B., 2015. Orchids of South Africa: A Field Guide. Struik, Cape Town
Crouch, N. R., Klopper, R. R., Burrows, J. E., Burrows, S. M., 2011. Ferns of Southern Africa: A comprehensive guide. Random House Struik, South Africa

Publicado el miércoles, 20 de abril de 2022 a las 01:15 PM por ludwig_muller ludwig_muller | 6 comentarios | Deja un comentario