Acacia anastomosa

General Plant Info

The botanical name is derived from the Greek anastomosis Italic text(formation of a network), in allusion to the reticulately nerved phyllodes.

Spindly, straggly, multi-stemmed shrubs 1–2 m tall. Bark smooth, brown. Branchlets angled at extremities but soon terete, marked with short, raised stem projections where phyllodes have fallen, finely ribbed (often appearing obscurely striate), the ribs dull or shiny (but lacking obvious resin) and of the same colour as the inter-rib spaces, dark red aging greyish, glabrous or with microscopic, red-brown glandular trichomes. Stipules mostly caducous, triangular, inconspicuous, c. 0.5 mm long. New shoots shiny, green except with minute, reddish brown glandular trichomes when very young. Phyllodes narrowly elliptic or sometimes obovate, mostly dimidiate with lower margin straight or shallowly convex and upper margin clearly convex, sometimes a few symmetric with both margins convex, (4–)5–9(–12) cm long, 15–25(–40) mm wide, sometimes interspersed with a few c. 10 mm wide, l: w = 2.5–4.5(–6), thinly to moderately coriaceous, straight or slightly recurved, green, glabrous; main longitudinal nerves 2–4 and normally with an additional 2 or 3 imperfect and/or less discrete nerves parallel to them, not especially prominent (but visible to the unaided eye), plane or slightly raised (when dry), yellow, not or scarcely resinous, some or all confluent with lower margin of phyllode for 2–12 mm above the pulvinus, minor nerves anastomosing to form an open, net-like reticulum, the nerve-islands ±irregularly square to oblong (longitudinally orientated), some or all nerves of the reticulum commonly lack capping cells and may therefore be somewhat obscure; marginal nerve discrete but not prominent, yellow to light brown, not or scarcely resinous; apices mucronate, the mucro triangular, 0.7–1.7 mm long, flattened (not noticeably thickened); pulvinus 2–3(–4) mm long

Gland situated on upper margin of phyllode at distal end of pulvinus or to 2 mm above it, sometimes absent, sometimes phyllode lamina slightly swollen about the gland. Inflorescences simple, 1 or 2(–3) per axil; peduncles 8–17 mm long, 0.6–0.8 mm diam. when in flower, to 1.5 mm diam. when in fruit, glabrous except often with scattered hairlets as on receptacle, striate by very fine, longitudinal furrows when dry; basal peduncular bract single, early caducous, triangular, c. 1 mm long; spikes 10–20(–28) mm long, with flowers rather close together; receptacles c. 1 mm diam., with microscopic, red-brown glandular trichomes. Bracteoles spathulate, 0.5–1 mm long, claws linear and expanded into ovate, slightly thickened laminae, some persistent on receptacle after flowers have dropped. Flowers 5-merous; calyx c. 1/3 length of corolla, gamosepalous, shortly dissected into triangular to broadly triangular or oblong lobes, calyx tube sparsely hairy (some glandular) to sub-glabrous and nerveless; corolla 1.5 mm long, glabrous or sub-glabrous but the nerveless or finely 1-nerved petals with microscopic white villae along their margins towards apices. Pods (dehisced valves plus few aborted, unopened pods) narrowly oblong to narrowly oblong-oblanceolate, narrowed towards the base, not constricted between the seeds, 5–10 cm long, 7–10 mm wide, crustaceous to ±sub-woody, straight, opening elastically from apex with the dehisced valves strongly recurved (often forming a ±open coil), dark brown and sometimes faintly pruinose, glabrous, obliquely nerved with some nerves sparingly anastomosing, inner surface of valves dark red except for yellow or light brown marginal nerve; marginal nerve thick and evident but not raised

Seeds (immature, few seen) oblique in the pods, seated in shallow but distinct chambers each separated by a narrow septum, ellipsoid; funicle-aril fleshy, white and narrowly turbinate, the funicle straight or sometimes convoluted

Geographic distribution

Occurs in the Kimberley region of northern Western Australia where it is known only from south of Kalumburu.

Grows on red volcanic soil in open woodland with Eucalyptus tectifica, Corymbia greeniana and Erythrophleum chlorostachys over Gossypium exiguum, Chrysopogon fallax and C. latifolius

Identification

Characteristic features. Spindly, predominantly glabrous shrubs. Phyllodes mostly dimidiate, moderately short and broad (mostly 5–9 cm long and 15–25 mm with l: w = 2.5–4.5), with 2–4 main longitudinal nerves (plus a few imperfect ones) of which some or all are confluent with lower margin of phyllode at base, minor nerves forming an open net-like reticulum comprising ±irregularly square to oblong nerve- islands, apical mucro short and not noticeably thickened. Inflorescences simple; peduncles 8–17 mm long; spikes short (10–17 mm long) and rather densely flowered. Flowers 5-merous; calyx c. 1/3 length of corolla, shortly dissected into triangular to broadly triangular lobes. Pods narrowly oblong to narrowly oblong-oblanceolate, narrowed towards the base, 5–10 cm × 7–10 mm, crustaceous to ±sub-woody, straight, opening elastically from apex with the dehisced valves strongly recurved (often forming a ±open coil); marginal nerve thick. Seeds oblique, seated in shallow but distinct chambers each separated by a narrow septum

Because of the paucity of collections it is not possible to determine an accurate phenology for this species; however, three specimens with flowers at anthesis have been collected, one in April, one in late May and the other in mid-June. The one known fruiting collection, with aborted and seemingly recently-dehisced pods, was collected in mid-October. This species therefore probably flowers at the end of the wet season and into the early dry season with fruit developing from the middle of the dry season

Links

http://florabase.dpaw.wa.gov.au/science/nuytsia/690.pdf

References

http://florabase.dpaw.wa.gov.au/science/nuytsia/690.pdf