Acanthaceae

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Acanthaceae

Description

Prostrate, erect or rarely, climbing, herbs or shrubs, or rarely small trees. Branches decussate, frequently angled, more rarely terete, often with transverse ridges across the node. Leaves opposite, subopposite or whorled (Crossandra), exstipulate, simple, usually with cystoliths (intercellular concretions, usually of calcium carbonate, which appear as white streaks on the upper surface), but lacking in Aphelandra, Gynocraterium, Nelsonia, Staurogyne, and Thunbergia, margins entire, crenate or undulate. Inflorescences axillary and/or terminal, flowers solitary or arranged in spikes, cymes or racemes, often densely clustered, frequently in axils of conspicuous bracts and with 2 bracteoles; bracts often leaf-like, sometimes enclosing corolla tube. Flowers zygomorphic to nearly actinomorphic, bisexual; calyx synsepalous at least basally, persistent, lobes 4 or 5, rarely (Thunbergia) an entire ring, or 12-20-lobed; corolla sympetalous, the limb 5-lobed or 2-lipped (rarely 1-lipped),lobes imbricate or contorted in bud, basally usually divided into a distinct narrow tube and wider throat; stamens 4, usually didynamous, or 2 fertile and sometimes accompanied by 1 or 2 staminodes, adnate to corolla tube, filaments free or basally connate in pairs, anther thecae usually 1 or 2, usually parallel, rarely divergent or transverse, muticous (without a projection), obtuse or rounded, or basally spurred, longitudinally dehiscent; pollen very varied in structure, striation and reticulation; disk annular and nectar-producing at base of ovary; ovary superior, 2-locular, either with 2 collateral (Thunbergia) or more commonly 2-10 superposed ovules per locule; placenta axile; style filiform, simple, stigma entire or more commonly 2-lobed, one lobe frequently smaller than the other. Fruits loculicidal, 2-valved capsules, frequently explosively dehiscent either on drying or on wetting, seeds usually borne on hook-like retinacula (funicles), these persistent in valves after seeds have been discharged or retinacula lacking (Gynocraterium, Staurogyne, Thunbergia); seeds 2-many, usually flattened, sometimes spheroidal (Gynocraterium, Staurogyne), testa smooth or roughened, sometimes with mucilaginous trichomes which expand when moistened.

Distribution

Guianas: present Pantropical: present pansubtropical: present temperate zones of both hemispheres: present
Pantropical and pansubtropical, sparingly distributed in temperate zones of both hemispheres; about 2500 species in about 250 genera; in the Guianas 83 species in 24 genera.

Lectotypifications:

  • Besleria surinamensis Miq.
  • Crossandra undulifolia Salisb.
  • Dipteracanthus canescens Nees
  • Dipteracanthus humilis Nees var. diffusus Nees
  • Dipteracanthus vindex Nees
  • Hygrophila conferta Nees
  • Leptostachya parviflora Nees
  • Leptostachya martiana Nees var. hispida Nees
  • Ruellia blechum L.
  • Staurogyne stolonifera (Nees) Kuntze
  • Thunbergia alata Bojer ex Sims
  • Thunbergia fragrans Roxb.

New combinations:

  • Justicia potarensis (Bremek.) Wassh.
  • Lepidagathis cataractae (Nees) Wassh.
  • Polylychnis radicans (Nees) Wassh.

New synonyms:

  • Arrhostoxylon rubrum (Aubl.) Nees var. attenuatum to Ruellia rubra Aubl.
  • Arrhostoxylon rubrum (Aubl.) Nees var. glomeruliflorum Bremek. to Ruellia rubra Aubl.
  • Arrhostoxylon rubrum (Aubl.) Nees var. multiflorum Bremek. to Ruellia rubra Aubl.
  • Arrhostoxylon rubrum (Aubl.) Nees var. parviflorum Bremek. to Ruellia rubra Aubl.
  • Arrhostoxylon rubrum (Aubl.) Nees var. pygmaeum Bremek. to Ruellia rubra Aubl.
  • Justicia cayennensis (Nees) Lindau var. parvifolia Bremek. to J. cayennensis (Nees) Lindau
  • Justicia martiana (Nees) Lindau to J. comata (L.) Lam.
  • Justicia parviflora (Nees) Lindau to J. comata (L.) Lam.
  • Justicia schomburgkiana (Nees) V.A.W. Graham to J. sphaerosperma Vahl
  • Lepidagathis surinamensis (Bremek.) Wassh. to L. cataractae (Nees) Wassh.
  • Polylychnis essequibensis Bremek. to P. radicans (Nees) Wassh.
  • Ruellia pipericaulis Rizzini to R. inflata Rich.
  • Ruellia radicans (Nees) Lindau to Polylychnis radicans (Nees) Wassh.
  • Ruellia ventricosa Poir. to R. inflata Rich.
  • Sericographis palustris Nees to Justicia laevilinguis (Nees) Lindau
  • Staurogyne linearifolia Bremek. to S. stolonifera (Nees) Kuntze
  • Stephanophysum cordifolium Mart. ex Nees to Ruellia inflata Rich.
  • Teliostachya coppenamensis Bremek. to Lepidagathis cataractae (Nees) Wassh.

New species:

  • Polylychnis ovata Wassh.

New name:

  • Justicia coppenamensis Wassh.

Wood



In this predominantly herbaceous family Trichanthera is the only genus in the Guianas with a true stem of over 10 cm in diameter. The other genera are mostly low shrubs with stems not exceeding a few cms in diameter. There was no wood available of all of these genera and only 5 out of a total of 24 can be treated here.
Growth rings absent or inconspicuous.
Vessels mostly in radial multiples of 2-4, occasionally more, in diffuse or more or less radial arrangement. Few in Trichanthera, very numerous and narrow in the other genera. Perforations simple. Intervascular pits alternate, very small, slits occasionally confluent; vessel/ray pitting identical or partly large and elongate (Polylychnis, Trichanthera). Tracheids present in the shrubby genera.
Rays 1-4-seriate or exclusively uniseriate (Justicia). Heterogeneous though with few rows of procumbent cells. In Justicia and Polylychnis exclusively square and upright cells (juvenile state). In Polylychnis and Trichanthera a number of cells contain cystoliths, in Trichanthera occasionally a rhombic crystal was also noticed.
Parenchyma almost absent, restricted to a few strands bordering a vessel. Strands often 2-3-celled, up to 6; also undivided, fusiform cells present.
Ground tissue in most genera septate fibres, thin-walled with a wide lumen, in Aphelandra and Justicia septate fibres absent or extremely rare. Pits simple, minute.

Notes

The genus Mendoncia is sometimes included in the ACANTHACEAE but is placed in the MENDONCIACEAE in this flora.