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Aerangis hildebrandtii

Aerangis hildebrandtii was original described by Reichenbach as Angraecum hildebrandtii (The Gardeners' Chronicle: A Weekly Illustrated Journal of Horticulture and Allied Subjects. 1878, Vol. 9, p. 725,  link).  It was transfered to genus Chamaeangis in 1972 (link), and to Microterangis in 1985.   More recently, it was transfered to Aerangis based on molecular phylogeny data (Cribb & Carlsward 2012).  It is a species found in Comoro Islands.

I got this plant from Andy's Orchids a couple years ago.  I'm growing at intermediate-warm temperature.  It seems to be able to grow fairly low light.  I might be giving too much light, and the leaves are a little yellowish.


Note that the middle and bottom flowers are missing the anther caps.




This species seems to be pretty similar to Aerangis hariotiana.  Both la Croix (2014, p.153-155) and Oviatt  & Nerison (2016) mentioned that they couldn't distinguish the two species reliably.  A photo in la Croix (2014) has a photo (by Gilles Grunenwald) with two species together, and it seems to show that the flower of A. hariotiana is slightly bigger. But Oviatt & Nerison (2016) observed that there appeared to be some individual variation of flower sizes within species, and other possibly distinguishing characters are also not too clear cut.  They mentioned that the most reliable difference is their fragrance.  I haven't found a literature which tells me how to distinguish them more completely, so I was curious to see the original description of A. hariotiana which was described as Mystacidium hariotianum (Journal de Botanique (Morot) 11: 153, 1897,  link).  I copied the description, and tried to translate it from Latin and French below.  However, I didn't find a definitive answer.

I found some DNA sequence data of the two species (Andriananjamanantsoa et al 2015, Andriananjamanantsoa et al 2016); two choloroplast genes and one nuclear ITS gene were sequenced.  The two species may not be identical in sequences, but the pattern seems to be a bit weird, and it isn't clear how diverged these two species are.  With 1342bp chloroplast matK, there are 8bp differences.  But these differences are all concentrated in a short region (position 567-648), and I suspect that they are the area where forward and reverse sequencing meet, so they might have low confidense in the region. With 887bp chloroplast trnL, one area at the very end shows a small difference.  677bp nuclear ITS1 sequnces are exactly same between the two species.

When they were scoring morphological characters, the two species were scored exactly same except the size; the size of plants are scored as large (15-35cm height and width) for A. hariotiana and medium (5-15cm H and W) for A. hildebrandtii. It appears that they used only one herbarium specimen in Kew per species, so it is not clear how applicable this size differences are in real world.  Finally, their measurment of flower sizes are idntical (2.18mm) for the two species, but the spur length differed (1.83mm for A. hariotiana and 2.01mm for A. hildebrandtii).


Original description:
MYSTACIDIUM HARIOTIANUM KRZL. N. SP.plu
Par M. F. KRAENZLIN.

Caulibus ascendentibus abbreviatis ; foliis oblongis apice bilobis, apicibus non divergentibus obtusis, ad 7 cm. longis, ad 3 cm. latis, crassiusculis; racemis quam folia subduplo longioribus tenuibus secundifloris; bracteis ochreatis apiculatis, quam ovaria multo brevioribus; sepalis e basi ovata triangulis acuminatis; petalis subbrevioribus ovatis obtusis; labello subæquali leviter excavato, calcari ipso paullulum incrassato; gynostemio brevissimo; anthera plana antice obtuse acutata infra obscure biloculari (diaphragmate vix evoluto) polliniis globosis, caudicula brevi lineari, glandula lata angusta. — Flores minutissimi 2 mm. diam. aurantiaci.

Insula madagascariensis. (In caldariis horti « Luxembourg » Parisiorum.)

Cette plante se rapproche beaucoup des Aeranthus erythropollinius Rchb. f. et xanthopollinius Rchb. f. (Mystacidium erythropollinium et xanthopollinium mihi) publiés dans le « Flora », 1865, p. 196. Elle diffère du Mystacidium xanthopollinium par ses grappes plus longues que les feuilles, par les sépales plus allongés, par son labelle ovate-oblong et non transversalement triangulaire, par son éperon obtus et non pointu, égalant mais ne dépassant pas l'ovaire, par son rostellum court et non prolongé en bec d'oiseau. Elle se rapproche du Mystacidium erythropollinium, tout en en différant par ses feuilles simplement bilobées et obtuses non divergentes-bilobées, et surtout par son labelle ovale à sommet non divisé en trois petits lobes.

Les autres caractères, et surtout l'aspect des grappes florales, sont tellement voisins de ceux qui appartiennent aux deux autres plantes ci-dessus mentionnées qu'il serait difficile d'en distinguer le M. Hariotianum. Les feuilles du M. erythropollinium sont plus nettement obovales ou cunéiformes; dans le M. xanthopollinium les grappes sont plus courtes que les feuilles. Si ce n'étaient les caractères propres à la fleur du M. Hariotianum, on pourrait faire de cette dernière plante une forme à grappes allongées du M. xanthopollinum.

Translation: (my comments are indicated by [])
Ascending and short stems; oblong leaves with the bilobbed apex and the tips of the lobes are not diverged and obtuse, up to 7cm long and 3cm wide, and thickish.  Inflorescences [recimes] almost twice longer than the leaves, and flowers in a row [I'm not sure if "secundifloris" is translated correctly].  Floral bracts ["bracteis ochreatis"=sheathing bract, which probably means floral bracts] are apiculate [with sharply pointed tips], and much shorter than the ovary. Sepals: from the ovate base, triangular shape acuminate tip [I'm not too sure about this translation].  Petal: shorter, ovate and obtuse.  Lip: nearly equal, slightly grooved ["subæquali leviter excavato"], spur very slightly thickened. Column: short.  Anther cap [I think "anthera plana" means this] is obtusely pointed, inside obscurely bilocular [has two chambers] (membrane is barely seen). Pollinia are globular.  The caudicle [stipe, stalk-like appendage of a pollinarium, connecting the pollinium and viscidium] is short-linear, and viscidium [the sticky part of a pollinarium] is narrow.  [Note "pollinarium" is a structure containing pollinia (pollen mass), cadicle (stripe), and viscidium.]

The flowers are tiny, 2 mm. diameter., and orange.

Madagascar island (The greenhouse of Luxembourg Garden, Paris [= Jardin du Luxembourg?])

This plant is very similar to Aeranthus erythropollinius Rchb. f. and A. xanthopollinius Rchb. f. (Mystacidium erythropollinium and M. xanthopollinium to me) published in Flora, 1865, p. 196. It differs from Mystacidium xanthopollinium by its longer raceme than the leaves, by the longer sepals, by its ovate-oblong and not transversely triangular labia, by its obtuse and non-pointed spur, equal to but not exceeding the ovary, by its rostellum short and not extended like beak of bird. It is close to Mystacidium erythropollinium, while differing in its leaves which are simply bilobed and obtuse non-divergent-bilobed, and especially in its oval labellum with an apex not divided into three small lobes.

The other characters, and especially the appearance of the floral raceme, are so close to those belonging to the two other plants mentioned above, that it would be difficult to distinguish the M. Hariotianum. The leaves of M. erythropollinium are more clearly obovate or wedge-shaped; in M. xanthopollinium the racemes are shorter than the leaves. If it were not for the characteristics of M. Hariotianum's flower, we could make this plant a form of M. xanthopollinum with elongated racemes.

Additional note by Naoki:
Aeranthus is Aeranthes, and the two species (Mystacidium erythropollinium and M. xanthopollinium) are now considered to be the same species and they are synonyms of Rhipidoglossum xanthopollinium.  From what we know now, it doesn't seem to be difficult to distinguish Aerangis hariotiana from Rhipidoglossum xanthopollinium.

According to Stewart et al. (2006, p.336-337), this species is actually from Comoro Islands (Grande Comore), same as A. hildebrandtii, not from Madagascar.


I'm starting to learn Latin a little bit, and following resources were useful.  I skimmed through Short and George (2013) to learn a little bit of grammar, and I found it to be really helpful to know the basics:

  • Short, E. and A. George 2013. A Primer of Botanical Latin with Vocabulary. Cambridge University Press (PDF)
  • Latin-is-Simple dictitonary (link)
  • Eckel, P.M. 2011. A Grammatical Dictionary of Botanical Latin. Missouri Botanical Garden.  (link)
  • Dictionary of botanical epithet.
  • Glossary of leaf morphology (Wikipedia)

Literatrure Cited:

  • Andriananjamanantsoa, H. N. (2015).  Systématique évolutive et Biogéographie de Angraecum(Orchidaceae, Angraecinae)à Madagascar. Ph.D Thesis, Université de Montréal (PDF)
  • Andriananjamanantsoa, H. N., Engberg, S., Louis Jr, E. E., & Brouillet, L. (2016). Diversification of Angraecum (Orchidaceae, Vandeae) in Madagascar: revised phylogeny reveals species accumulation through time rather than rapid radiation. PloS one, 11(9): e0163194. (link to full text)
  • Cribb, P., & Carlsward, B. (2012). New combinations in Aerangis, Diaphananthe and Podangis (Orchidaceae, subtribe Angraecinae). Phytotaxa, 71(1), 42-47.
  • la Croix, I. 2014. Aerangis. Timber Press, Portland, Oregon.
  • Oviatt, B., and B. Nerison, 2016, Aerangis hariotiana.  Orchids August: 590-595. (link to pdf)
  • Stewart, J., J. Hermans and B. Campbell. 2006. Angraecoid Orchids: Species from the African Region. Timber Press, Portland, Oregon.



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