Stenosiphonium wightii, copyright Flowers of India.

Belongs within: Acanthaceae.
Contains: Andrographinae, Barleria, Lepidagathis, Justiciinae, Ruellia, Strobilanthes, Petalidium.

The Acanthoideae are a subgroup of the flowering plant family Acanthaceae characterised by fruits that are explosive capsules, with seeds bearing a small, hooked stalk (retinaculum) that ejects them from the capsule (Scotland & Volleson 2000).

Of shrimp plants and bear’s breeches
Published 17 April 2017

For today’s semi-random post, I drew the plant subfamily Acanthoideae. As recognised by Scotland & Vollesen (2000), the Acanthoideae is the largest of the subfamilies of the Acanthaceae by a considerable margin, including about 95% of the family’s 2500+ species. Though perhaps not hugely familiar to readers in more temperate climes, the Acanthoideae are one of the dominant groups of herbs and shrubs in tropical parts of the world.

Golden shrimp plant Pachystachys lutea, copyright Dryas.

The Acanthoideae have been recognised as a morphological group since the late 1800s and their integrity has been confirmed by more recent molecular studies. They are distinguished from related plants (within the Lamiales, the order that also includes such plants as the mints and snapdragons) by having capsular fruits that dehisce explosively when mature to scatter their seeds. The seeds are attached within the capsule by hook-shaped stalks called retinacula that presumably play a role in determining how the seeds are released. A classification of Acanthaceae published in 1965 by Bremekamp restricted the family to species with explosive fruits and retinacula, dividing them between two subfamilies, the Acanthoideae and Ruellioideae, based on the absence or presence, respectively, of cystoliths. These are outgrowths of the epidermal cell walls that are impregnated with calcium carbonate. They are visible in the stems and leaves, at least in dried specimens, as hard white streaks. As phylogenetic studies have supported division of Acanthoideae in the broad sense between a cystolith-possessing and a cystolith-lacking clade, the decision whether to recognise ‘Ruellioideae’ as a separate subfamily comes down to a ranking choice only. At lower levels, the classification of Acanthoideae is less straightforward. Over two hundred genera of Acanthoideae are recognised but just three of those—Justicia, Strobilanthes and Ruellia—account for about half the total number of species. Each of these mega-genera is morphologically diverse and likely to be para- or polyphyletic with regard to related taxa, raising the distinct likelihood of future revisions.

Spiny bear’s breeches Acanthus spinosus, copyright Magnus Manske.

Economically, few of the Acanthoideae are of great significance except for a number of species being grown ornamentally. One such species is Acanthus mollis, which goes by the vernacular name of ‘bear’s breeches’ (why, I have absolutely no idea). Acanthus was a popular decorative motif in classical Greece and forms the basis for the design of Corinthian columns. Its use as an ornamental has lead to it becoming regarded as an invasive weed in some regions, largely because this is one of those garden plants that Just Will Not Die, spreading easily from seeds and tubers. We’ve got some in a pot outside that is currently flourishing despite having been burnt down to a nub by the searing Perth summer sun, metaphorically shouting its defiance at an uncaring world.

Systematics of Acanthoideae
<==Acanthoideae [Imbricatae]K08
    |    |  i. s.: Acanthopsis hoffmannseggianaSV00
    |    |         AchyrocalyxSV00
    |    |         Blepharis [incl. Acanthodium, Blepharacanthus, Trichacanthus]SV00
    |    |           |--B. feroxCV06
    |    |           |--B. fleckiiCV06
    |    |           |--B. giganteaCV06
    |    |           |--B. linariaefoliaPP07
    |    |           |--B. maderaspatensisHK98
    |    |           |--B. meyeriCV06
    |    |           |--B. pruinosaCV06
    |    |           `--B. spinifexCV06
    |    |         CrossandrellaSV00
    |    |         CynarospermumSV00
    |    |         CyphacanthusSV00
    |    |         EncephalosphaeraSV00
    |    |         GeissomeriaSV00
    |    |         Holographis [incl. Berginia, Lundellia, Pringleophytum]SV00
    |    |         Neriacanthus [incl. Aphanandrium]SV00
    |    |         OrophochilusSV00
    |    |         Rhombochlamys [Rhombochlamydeae]SV00
    |    |         Salpixantha [=Salpingantha, Salpinxantha]SV00
    |    |         Sclerochiton [incl. Butayea, Isacanthus, Pseudoblepharis]SV00
    |    |           `--S. ilicifoliusSV00
    |    |         StrobilacanthusSV00
    |    |         XantheranthemumSV00
    |    |--+--Stenandrium [incl. Stenandriopsis; Stenandriopsideae]SV00
    |    |  `--Aphelandra (see below for synonymy)SV00
    |    |       |  i. s.: A. cristataT-W89
    |    |       |         A. fascinatorT-W89
    |    |       |         A. scabraSV00
    |    |       |         A. sinclairianaF11
    |    |       |--A. boyacensisSV00
    |    |       |--A. dolichanthaSV00
    |    |       `--+--A. campanensisSV00
    |    |          `--A. leonardiiSV00
    |    `--+--Crossandra [incl. Harrachia, Pleuroblepharis, Polythrix]SV00
    |       |    |--C. infundibuliformisSV00
    |       |    |--C. niloticaSV00
    |       |    `--C. pungensSV00
    |       `--Acanthus [incl. Cheilopsis]SV00
    |            |--A. ebracteatus Vahl 1791HS14
    |            |--A. ilicifoliusBR65
    |            |--A. mollisC55
    |            |--A. montanusSV00
    |            `--A. spinosus Linnaeus 1753PL04
    `--Ruellieae [Hygrophileae, Petalideae, Ruellioideae, Strobilantheae]K08
         |  `--Barleriinae [Barlerieae, Lepidagathideae]K08
         |       |--BarleriaSV00
         |       |--LepidagathisK08
         |       |--Barleriola solanifoliaK08, SV00
         |       |--BorneacanthusK08
         |       |--Chroesthes lanceolataK08, SV00
         |       |--Hulemacanthus novoguineensisK08, SV00
         |       |--BoutoniaK08 [incl. PeriblemaSV00]
         |       |    `--B. cuspidataSV00
         |       `--CrabbeaK08
         |            |--C. reticulataSV00
         |            `--C. velutinaSV00
            `--Ruelliinae [Hygrophilinae, Petalidiinae, Strobilanthinae, Trichanthereae]SV00
                 |--Dischistocalyx hirsutusSV00
                 |--Trichanthera giganteaSV00, DP72
                 |--Calacanthus dalzelliana [incl. Lepidagathis grandiflora]SV00
                 |--Mimulopsis solmsiiSV00, DVC08
                 |--Strobilanthopsis [incl. Pseudacanthopale]SV00
                 |--Carvia callosaSV00, VD03b
                 |--Sericocalyx crispus (Linnaeus) Bremekamp 1944SV00, VD03a [=Ruellia crispa Linnaeus 1753VD03a]
                 |--Satanocrater [incl. Haemacanthus]SV00
                 |    `--S. paradoxaE09
                 |--Blechum [Blechinae]SV00
                 |    `--B. pyramidatumSV00
                 |--Bravaisia [incl. Androcentrum, Onychacanthus]SV00
                 |    `--B. berlandierianaSV00
                 |--Brillantaisia [incl. Belantheria, Leucoraphis, Ruelliola]SV00
                 |    `--B. lamiumSV00
                 |--Dyschoriste [incl. Calophanes]SV00
                 |    `--D. vagansSV00
                 |--Eremomastax [incl. Paulowilhelmia]SV00
                 |    `--E. polyspermaSV00
                 |--Mellera [incl. Onus]SV00
                 |    `--M. lobulataSV00
                 |--Phaulopsis [=Phaylopsis]SV00
                 |    `--P. imbricataSV00
                 |--Epiclastopelma [incl. Sooia]SV00
                 |    `--E. macranthumSV00
                 |--Louteridium [incl. Neolindenia; Louterideae]SV00
                 |    `--L. donnell-smithiiSV00
                 |--Physacanthus [incl. Haselhoffia; Haselhoffieae]SV00
                 |    `--P. batanganusSV00
                 |--Sanchezia [incl. Steirosanchezia]SV00
                 |    |--S. nobilisSV00
                 |    `--S. speciosaSV00
                 |    |--B. acaulisB00
                 |    `--B. australisB00
                 |    |--C. difformisP03
                 |    `--C. trifloraVD03a
                 |--Eranthemum [incl. Daedalacanthus]SV00
                 |    |--E. nervosumSV00
                 |    |--E. pulchellumSV00
                 |    `--E. purpurascensP03
                 |    |--A. aethio-germanica Ensermu 2009E09
                 |    |--A. confertifloraSV00
                 |    |--A. laxifloraE09
                 |    `--A. pubescensE09
                 |--Hygrophila [incl. Asteracantha, Hemiadelphis, Kita, Nomaphila, Plaesianthera, Santapaua, Synnema]SV00
                 |    |--H. angustifoliaB00
                 |    |--H. auriculataSV00
                 |    |--H. corymbosaSV00
                 |    |--H. gracillimaCV06
                 |    |--H. polyspermaM72
                 |    `--H. schulliVB02
                 |--Hemigraphis [incl. Gantelbua]SV00
                 |    |--H. alternataB00
                 |    |--H. colorataSV00
                 |    |--H. duraVD03a
                 |    |--H. hirtaVD03a
                 |    |--H. latebrosaVD03a
                 |    |    |--H. l. var. latebrosaTS72
                 |    |    `--H. l. var. heyneanaTS72
                 |    `--H. venosa Clarke 1884 [=Ruellia venosa Heyne ms]VD03a
                      |--S. confertumVA06
                      |--S. cordifolium [incl. S. cordifolium var. subsericeum, S. russellianum var. subsericeum]VA06
                      |--S. parviflorumVA06
                      |--S. russellianumVA06
                      |--S. setosumVA06
                      `--S. wightii Bremekamp 1944VA06
Acanthoideae incertae sedis:
  Chlamydacanthus [incl. Theileamea]SV00
    `--C. euphorbioidesSV00
    |--L. barteriSV00
    `--L. elegansSV00
  Lasiocladus [incl. Synchoriste]SV00
  Neuracanthus [incl. Leucobarleria]SV00
    `--N. sphaerostachysS72
  Whitfieldia [incl. Leiophaca, Pounguia, Stylarthropus; Whitfieldieae]SV00
    |--W. elongataSV00
    |--W. lateritiaSV00
    `--W. preussiiSV00

Aphelandra [incl. Amathea, Hemisandra, Hydromestus, Lagochilium, Lepidacanthus, Odontophyllum, Sreemadhavana, Strobilorhachis, Synandra; Aphelandreae]SV00

*Type species of generic name indicated


[BR65] Black, J. M., & E. L. Robertson. 1965. Flora of South Australia. Part IV. Oleaceae–Compositae. W. L. Hawes, Government Printer: Adelaide.

[B00] Braby, M. F. 2000. Butterflies of Australia: their identification, biology and distribution vol. 2. CSIRO Publishing: Collingwood (Victoria).

[C55] Candolle, A. de. 1855. Géographie Botanique Raisonée: Ou exposition des faits principaux et des lois concernant la distribution géographique des plantes de l’époque actuelle vol. 2. Librairie de Victor Masson: Paris.

[CV06] Craven, P., & P. Vorster. 2006. Patterns of plant diversity and endemism in Namibia. Bothalia 36 (2): 175–189.

[DVC08] Darbyshire, I., K. Vollesen & H. M. Chapman. 2008. A remarkable range disjunction recorded in Metarungia pubinervia (Acanthaceae). Kew Bulletin 63 (4): 613–615.

[DP72] Deighton, F. C., & K. A. Pirozynski. 1972. Microfungi. V. More hyperparasitic hyphomycetes. Mycological Papers 128: 1–110.

[E09] Ensermu K. 2009. Three new species of Acanthaceae from Ethiopia. Kew Bulletin 64 (1): 57–65.

[F11] Fraga, R. M. 2011. Family Icteridae (New World blackbirds). In: Hoyo, J. del, A. Elliott & D. A. Christie (eds) Handbook of the Birds of the World vol. 16. Tanagers to New World Blackbirds pp. 684–807. Lynx Edicions: Barcelona.

[HK98] Hahn, A., & H. Kusserow. 1998. Spatial and temporal distribution of algae in soil crusts in the Sahel of W Africa: Preliminary results. Willdenowia 28: 227–238.

[HS14] Huisman, J. M., & A. Sampey. 2014. Kimberley marine biota. Historical data: marine plants. Records of the Western Australian Museum Supplement 84: 45–67.

[K08] Kameyama, C. 2008. New species, nomenclatural changes and lectotypifications in Neotropical Lepidagathis Willd. (Acanthaceae). Kew Bulletin 63 (4): 565–581.

[M72] Mitra, S. N. 1972. Observations on the vegetation of the Upper Damodar catchment area. Journal of the Bombay Natural History Society 69 (1): 17–25.

[PP07] Pandey, R. P., & P. M. Padhye. 2007. Studies on phytodiversity of Arid Machia Safari Park-Kailana in Jodhpur (Rajasthan). Bulletin of the Botanical Survey of India 49: 15–78.

[P03] Paul, T. K. 2003. Botanical observations on the Purulia pumped storage hydropower project area, Bagmundi Hills, Purulia district, West Bengal. Bulletin of the Botanical Survey of India 45: 121–142.

[PL04] Pohl, G., & I. Lenski. 2004. Zur Verbreitung und Vergesellschaftung von Pennisetum orientale Rich. in Nordeuböa (Griechenland) (Poaceae, Paniceae). Senckenbergiana Biologica 83 (2): 209–223.

[S72] Satakopan, S. 1972. Keys to the identification of plant remains in animal droppings. Journal of the Bombay Natural History Society 69 (1): 139–150.

[SV00] Scotland, R. W., & K. Vollesen. 2000. Classification of Acanthaceae. Kew Bulletin 55 (3): 513–589.

[T-W89] Tenison-Woods, J. E. 1889. On the vegetation of Malaysia. Proceedings of the Linnean Society of New South Wales, series 2, 4 (1): 9–106, pls 1–9.

[TS72] Thaker, D. N., & S. D. Sabnis. 1972. Occurrence of Cochlearia cochlearioides (Roth) Sant. & Mah. & Campanula benthamii Wall. ex Kitamura in Gujarat State, India. Journal of the Bombay Natural History Society 69 (1): 227–229.

[VA06] Venu, P., & W. D. Albertson. 2006. The identity of Stenosiphonium wrightii Bremek. (Acanthaceae). Bulletin of the Botanical Survey of India 48: 211–216.

[VD03a] Venu, P., & P. Daniel. 2003a. Is Hemigraphis venosa C.B. Clarke (Acanthaceae) extinct? Bulletin of the Botanical Survey of India 45: 91–96.

[VD03b] Venu, P., & P. Daniel. 2003b. What is Kanjarum palghatense Ramam. (Acanthaceae)? Bulletin of the Botanical Survey of India 45: 97–104.

[VB02] Vijay, S. K., & T. N. Bhardwaja. 2002. Vegetation and phenodynamics of wetlands of central Rajasthan. Journal of the Bombay Natural History Society 99 (3): 573–581.

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