53 New species of Acacia (Fabaceae, Mimosoideae) from tropical Australia Mary D. Tindale and Phillip G. Kodela Abstract Tindale, Man/ D. & Kodela, Phillip G. (National Herbarium ofNeiv South Wales, Royal Botanic Gardens, Mrs Macquaries Road, Sydney, NSW, Australia 2000) 1992. New species of Acacia (Fabaceae, Mimosoideae) from tropical Australia. Telopea 5C1): 53-66. Acacia arafurica, A. cataractae, A. delicatula, A. gracilenta and A. brockii from the north of Western Australia and the Top End of the Northern Territory are described and illustrated. Although some of these species occur in national parks, several have restricted distributions and should be considered especially in the management plans of Kakadu and Katherine Gorge National Parks. Introduction In the last decade or so the Top End and Kimberley regions of northern Australia have been more widely explored, resulting in the discovery of many new plant spe¬ cies. Several of these species are described here, so that they may be published prior to the forthcoming volume on Acacia in the Flora of Australia. Further collections are required to provide more information on taxonomic variation, distributions and ecol¬ ogy, since existing specimens are often in limited numbers or concentrated from more accessible areas. Recent findings of new taxa emphasise our limited current knowledge of these areas and the potential of future discoveries, which need to be considered in the management of National Parks and future planning for mining and tourism in the region. The terminology of shapes in the descriptions of species is that defined by Lee (1948: 144). The diameter of flower-heads is only given as a guide, since it is often affected by the degree of pressure on the specimens during drying. Sect. Plurinerves (Benth.) Maiden & Betche, Triangulares group 1. Acacia arafurica Tind. et Kodela, sp. nov. Ab Acacia sublanata Benth. differt phyllodiis crassioribus, 15-34 mm longis, 9-25 mm latis, inflorescentiis spicatis, 10-21 mm longis et pedunculis 2-5 mm longis. Type: Northern territory: Arnhem Land, Anguldili Creek, Murgenella Road, 11°45'S, 133°10'E, R. Hinz 2, 25 May 1988; holo NSW 235594; iso BRI, CANB, DNA 32714, K, PERTH. Rounded shrub to 3 m high. Branchlets terete, light brown or greyish brown, with a rusty or greyish hue resulting from the indumentum which is sparsely to densely pubescent to cobwebbed (the hairs hyaline, white and/or fawn, often curled, to 0.5 mm long, sometimes intermixed with red-brown papillose hairs); longitudinal ridges to 0.2 mm high. New shoots and young foliage reddish brown, resinous, cobwebbed. Pltyllodes borne singly, subsessile, obliquely ovate-rhomboidal, asymmetrical, the lower margin almost straight to slightly curved, the upper margin abruptly curved to more 54 Telopea Vol. 5(1): 1992 than 90° near pulvinus, then curved to apex, 1.5-3.4 cm long, 0.9-2.0(-2.5) cm wide, flat, coriaceous, with a sparse to moderate cover of nonglandular, erect to sub- appressed hairs to 0.5(-0.7) mm long (the hairs being similar to those on the branch- lets), with (3—)4(—5) prominent longitudinal nerves, the minor nerves strongly reticu¬ late, the margin thickened, often wavy when dry, the mucro minutely glanduliferous, acuminate, pungent, straight or oblique, 0.4-1.2 mm long; gland on the upper margin of the phyllode prominent, 1,6-2.5(-5.0) mm above the pulvinus, orbicular to elliptical, pale yellow, glabrous, 0.4-0.6 mm long, 0.3-0.5 mm wide, the orifice < 0.1 mm in diam.; pulvinus 0.5-1.2 mm long, cobwebbed-pubescent; stipules lanceolate to narrow- ovate, 1.5-2.1 mm long, glabrous or ciliolate with hairs to 0.4 mm long, striate with several nerves arising from the base, the apex acute to acuminate. Inflorescences spi- cale, borne singly or very rarely in pairs in the axils of the phyllodes, (10—)15—21 mm long, 4.0-5.5 mm wide, golden yellow; peduncles 2-5 mm long, moderately to densely pubescent; brcicteoles composed of a narrow deltate lamina 0.6-1.1 mm long (the pointed apex longer than the young flower buds), with white hairs to 0.2 mm long on the margin, attached perpendicularly to a glabrous claw 0.2-0.6 mm long. Flowers 5- merous; calyx membranous, 0.5—0.8(—1.1) mm long, dissected for 1/3-1/2 its total length, with faint midribs or keeled, the apices ciliolate with hairs to 0.2 mm long, otherwise glabrous; corolla 1.1—1.4(—1.8) mm long, resinous, dissected for 1 /3-1 /2 its length, the petals oblanceolate to narrow-obovate, glabrous, with a midrib, the apices thickened, incurved and often cucullate, darker than the rest of corolla; stamens with filaments to 3.6 mm long; ovary ± oblong or narrow-obovate, red-brown, densely pubescent with white hairs to 6.25 mm long; style eccentric, to 2.7 mm long, often curled. Legumes linear, tapering gradually at both ends, ± straight, constricted between the seeds, 6.5-10.5 cm long, (2.5-)4.0-4.5 mm wide, chartaceous, raised and longitu¬ dinally ribbed over seeds, clothed with oppressed to erect, white, usually interwoven hairs to 0.5 mm long. Seeds 4-7 arranged longitudinally in the legume, (5.2-)6.0-7.0 mm long, 2.1-3.1 mm wide, black, glossy; pleurogram open, very slightly constricted towards the hilum; areole same colour as the rest of the seed, 3.8-5.3 mm long, 0.9-1.3 mm wide; funicle cream-coloured, expanded into a turbinate aril, folded c. 3 times beneath the seed (only one specimen with fruit and seeds was examined). Flowering April-May, July. Fruiting September. Figure 1. Distribution: Northern Territory: Darwin and Gulf District: Cobourg Peninsula southeast to Maningrida and Nabarlek. Figure 2. Habitat: In sandy soil on coastal river flats or near streams in the gorge country of the inland, sometimes in tall open forest. Often in swampy areas. Etymology: The specific epithet refers to the Arafura Sea which lies to the north of the region in which A. arafurica occurs. Notes: R. Hinz uses the collecting number '2' for two separate specimens (including the specimen we have chosen as holotype, i.e. NSW 235594), possibly applying the number to indicate that they are the same species. We are following Pedley's classification (1987) where Acacia sublanata has been re¬ ferred to the Triangulares group in sect. Plurinerves, whereas Cowan & Maslin (1990) placed A. sublanata with A. deltoidea Cunn. ex Don and its allies in sect. Plurinerves. Acacia sublanata Benth., which occurs in the Top End of the Northern Territory, is allied to A. arafurica which has very similar flowers, but there are differences in the phyllodes and shape of inflorescences. In A. sublanata the inflorescences are globular or rarely shortly oblong (Pedley 1987: 319, Figure 2f) whereas in A. arafurica they are spicate (Figure la). In A. sublanata the minor reticulate nervation is less distinct and Tindale & Kodela, Acacia 55 the areolae more acute, running ± parallel with the main nerves, whereas the phyl- lodes of A. amfurica are larger and slightly thicker with a strong reticulate network between the main nerves (Figure lb). The phyllodes of A. sublanala are mostly broadest at or above the middle (as stated by Cowan & Maslin 1990). This is partic¬ ularly noticeable in the specimens of A. sublanata with larger phyllodes, e.g. Macon- ochie 1519, but this is not always the case, e.g. Slee &r Craven 3078, whereas in A. arafurica they are broadest at or below the middle. Pedley (1987) describes the legumes of A. sublanata (under Racosperma sublanatum (Benth.) Pedley) as 'glabrous'. In the material of A. sublanata that we have examined, e.g. v. Balgooy 1310 & Byrnes, Lazarides & Adams 171, Maloney NSW 126756, Must 771, Craven 6068 and Slee & Craven 3078, the legumes are pubescent, although in Specht 819 the fruit is subglabrous. Specimens examined: Northern Territory: Darwin and Gulf District: 12 km N Three Ways, Co- bourg Peninsula, 11°13'S, 132°17'E, Sivertsen 793, 29 May 1983 (DNA 24309, PERTH); near Tomkinson River, Maningrida, Brigden, Apr 1972 (BRI, DNA D4432); Nabarlek, 12°2TS, 133°20'E, Hinz 2, 3 Apr 1988 (BRI, DNA 31436, MEL); Arnhem Land, Maningrida, 12°30'S, 134°17'E, Coleman 31, 25 Sep 1988 (DNA 36642). Figure 1. A. arafurica. a, habit study with spicate inflorescences; b, upper portion of phyllode; c, legume; d, seed (a,b, Sivertsen 793; e,d, Coleman 31). a,c, scale bar = 1 cm; b,d, scale bar = 5 mm. 56 Telopea Vol. 5(1): 1992 Figure 2. Distribution of Acacia arafurica ((cid:9633)), A. cataractae ((cid:9733)), A. delicatula (O), A. gracilenta (A) and A. brockii (• ) . Key to A. arafurica and A. sublanata 1 Phyllodes (2.5-)5-13(-24) mm long, (1.5—)3-10(—14) mm wide, thinly coriaceous. Inflorescences mostly globular, (4.5-)6-7 mm in diam. or sometimes oblong. Peduncles (4-)7-15(-20) mm long . A. sublanata 1* Phyllodes 15-34 mm long, 9—20(—25) mm wide, coriaceous. Inflorescences spicate, (10—)15—21 mm long. Peduncles 2-5 mm long . A. arafurica Acacia stigmatophylla Cunn. ex Benth. group 2. Acacia cataractae Tind. et Kodela, sp. nov. Acacia cataractae: A. stigmatophyllae Cunn. ex Benth. affinis, a qua differ! phyllodorum nervis 1-3 longitudinalibus margine inferiore plerumque confluentibus, calycibus 0.75- 1.0 mm longis, 2/3 partibus vel ad basin dissectis et petalis costa inconspicua. Type: Northern Territory: Above U.D.P. Falls [Gunlom Falls, on Waterfall Creek], C.H. Cittins 2851, 3 May 1975; holo NSW 236250; iso BRI, CANB, DNA, K. Shrub to 2 m high; bark brown, fibrous. Brancldets markedly angled to almost flat¬ tened towards apices, greenish brown to mid-brown, glabrous, with resinous, minutely Tindale & Kodela, Acacia 57 crenulated ridges to 0.3(-0.5) mm high. New shoots and young foliage yellowish green, resinous particularly towards apices. Phyllodes borne singly, oblanceolate to narrow- oblanceolate or very narrow-elliptical, sometimes slightly asymmetrical, straight or very slightly curved, (3.5-)4.0-10.5 cm long, (6.5-)7.5-20.0(-23.0) mm wide, (3-)4-8 times as long as wide, grey-green, mid-green or dull dark green, flat, thinly coriaceous, glabrous, the margins nerve-like, crenulated with resin, with 3 prominent longitudinal nerves pale yellow, 2 of these reaching the base while the other usually confluent with the lower margin 0.5-1.7 cm from the pulvinus, sometimes with 4 subprominent longitudinal nerves, all other nerves faint with moderate anastomosing, 1-4 nerves per mm of phyllode width (longitudinal wrinkling produces a fine striated appear¬ ance); apex obtuse, often asymmetrically refuse or truncate, with a blunt, red-brown mucro 0.3-0.7 mm long, the gland minute; basal gland prominent, a ± elliptical swell¬ ing on the upper margin just above the pulvinus, (0.8—)1.5-2.6 mm long, 0.4-1.2 mm wide, glabrous, with a ± circular, slightly exserted, pale yellow lip c. 0.2 mm wide, the ± circular orifice to 0.2 mm in diam.; pulvinus (0.5—)1.0—2.5(—3.5) mm long, gla¬ brous, often mealy; stipules deltate, 0.7-1.2 mm long, often somewhat mealy. Inflo¬ rescences spicate, borne singly or in twos or threes in the upper axils of the phyllodes (when in threes the spikes are often at different stages of development), (10—)14—50 mm long, (4.5-)5.5-7.5 mm wide, usually dense, yellow or bright to golden yellow, often densely mealy between flowers; buds obovate to very broad-obovate, very res¬ inous; peduncles 4-12 mm long, glabrous, resinous. Floiuers 5-merous; calyx membra¬ nous, 0.75-1.0 mm long, deeply cut to c. 2/3-3/4 its length, the sepals often ± free, 0.1-0.2 mm wide, with a faint midrib, glabrous, the apex usually rounded; corolla 1.0- 1.5 mm long, dissected 1 /3—1 /2 its length, glabrous, the petals elliptical to almost broad-elliptical or narrow-ovate, with a faint midrib, often mealy, often resinous, the apex acute; stamens with filaments to 3.2 mm long; ovary oblong to elliptical, granular, pubescent (especially towards the apex) or almost glabrous with a few minute hairs towards apex; style to 3.5 mm long. Legumes very narrow-oblanceolate (rarely linear), the base tapering gradually, straight or very slightly curved, 2.6-5.0 cm long, 4-7(-9.5) mm wide, straight-sided, woody, flat, slightly raised over the seeds, brown (greenish brown when young), glabrous, often scurfy, resinous (especially when young), the margins thickened, the surface with conspicuous diagonal nerves and some anasto¬ mosing, opening elastically from the apex, the apex ± hooked. Seeds 7-13 obliquely arranged in the legume, ellipsoid or oblongoid, sometimes ± rhomboidal, (2.7-)3.0- 4.0(—5.3) mm long, 1.3-2.0 mm wide, brown, glossy; pleurogram open and slightly constricted towards the hilum; areole the same colour or slightly darker than rest of the seed, (1.8-)2.3-3.1(-4.2) mm long, 0.7-0.9 mm wide, often with a pale halo; funicle expanded into a cupular aril beneath the seed, the combined funicle-aril cream- coloured to tawny, narrowly turbinate. Flowering late December-January, March-July. Fruiting March-May. Figure 3a-e. Distribution: Northern Territory: Darwin and Gulf District: From Bathurst Island and the Maningrida area, south to Umbrawarra Gorge (13°58'S) near Pine Creek. Recorded in Kakadu National Park at Gunlom Falls, Graveside Gorge and Billiard Creek Road. Figure 2. Habitat: Usually found on sandy soil near streams in sandstone plateau-gorge coun¬ try or on coastal plains, mostly in Eucalyptus woodland amongst rocks and boulders. Etymology: The epithet refers to Waterfall Creek at Gunlom (U.D.P.) Falls, about 15 km NW of El Sharana, where this species is locally abundant. Notes: It is a member of the A. stigmatopln/lla Cunn. ex Benth. group, which connects the Juliflorae with the Plurinerves (Tindale 1980). A. stigmatophyUa is common in the Top End of the Northern Territory and in the Kimberley, Western Australia. 58 Telopea Vol. 5(1): 1992 A. cataractae has been confused with other tropical Australian species, viz. A. limbata F. Muell. (Kimberley, W.A., northern N.T. and north-western Queensland) and A. lazaridis Pedley (northern Queensland). The latter two species have larger legumes and seeds, longer peduncles (except in Adams 1138), more asymmetrical phyllodes and cupular calyces that are dissected for f /4—1 /3 of their length. A. lazaridis usually has longer flowers than the other two species. Selected specimens: Northern Territory: Darwin and Gulf District: Bathurst Island, 11°45'S, 130°35'E, Stevenson 159, 28 Dec 1975 (DNA); Maningrida area, I2°02'S, 134°17’E, Clark 1306, 26 Jul 1987 (BRI, DNA); Kakadu, Graveside Gorge 13°19'S, 132°33'E, Brock 190, 30 Dec 1986 (DNA); U.D.P. Falls, Sth Alligator R., Byrnes 1783, 4 Mar 1970 (BRI, DNA, K, NSW, NT); Kakadu National Park: U.D.P. Falls area: 0.7 km upstream from the top of falls, on Waterfall Creek, 13°25'S, 132;>24'E, Sice & Craven 3045, 30 Apr 1990 (CANB, NSW); Waterfall Creek, Hancock 364, 26 May 1991 (CANB, DNA, K, NSW, PERTH); Kakadu National Park, Billiard Creek Road, 13°30'S, 132°14'E, Menkhorst 297, 4 Mar 1989 (DNA); road to Umbrawarra Gorge, 13°56'S, 131°45'E, Brock 205, 13 Jan 1987 (DNA); Umbrawarra Gorge Rd, 13°58'S, 131°40'E, Brock 94, 13 Mar 1986 (DNA). 3. Acacia delicatula Tind. et Kodela, sp. nov. Acacia delicatula: A. subternatae F. Muell. affinis, sed phyllodiis linearibus-filiformibus, semiteretibus, 0.2-0.5 mm latis, capitulis 4.0-6.5 mm diametro, calycibus 0.6-1.0 mm longis, ad dimidiam vel plus dissectis, sepalorum apicibus plus minusve subulatis vel acuminatis et corollis 1.3-1.75 mm longis. Type: Northern Territory: 2.7 km W of 'Rock Pools' (Bulbe gardar) along high track skirting the base of 'Geringbah' Escarpment [SW of Cahills Crossing], 12°28'S, 132°55'E, C.F. Puttock & J.T. Waterhouse, 24 July 1980; holo NSW 237163; iso DNA, K, UNSW 10162. Erect to ascending, often spreading, resinous shrub to 1.5 m high, branching from the base; bark finely fissured. Branchlets ± terete, striated, becoming markedly angular towards apices, light brown to brown, sometimes grey or greenish brown, glabrous, sometimes mealy, often resinous, the minutely crenulated ridges to 0.2 mm high. Phyllodes single or in clusters of 2-6, linear to filiform, semiterete, (4.5—)7—13(—18) mm long, (0.2-)0.3-0.4(-0.5) mm wide, straight or slightly curved, glabrous, nerves incon¬ spicuous, the mucro acute to ± aristate, often fawn-coloured, straight or oblique, to 0.5 mm long, bearing a minute gland. Capitula borne singly, 4.0-6.5 mm diam.; peduncles (5—)8—15(—18) mm long. Flowers 5-merous, 34-38 per capitulum; calyx 0.6-1.0 mm long, dissected for 1/2-3/4 of its length, glabrous, the sepals 0.1-0.2 mm wide, usually with ± subulate to acuminate apices; corolla c. twice the length of the calyx, 1.3-1.75 mm long, dissected by 1/2 or more of its length, the petals very narrow- elliptical to narrow-lanceolate or narrow-oblanceolate, 0.2-0.4 mm wide, glabrous, with a distinct midrib, the apex thickened and often cucullate; stamens with filaments to 3 mm long; ovary glabrous, usually with a bulbous yellow cap on the summit. Legumes straight-sided or slightly indented between the.seeds, very narrow-oblan¬ ceolate or sometimes ± linear, basally tapered, (2.0-)3.0-4.0(^1.4) cm long, 3-4 mm wide, flat, woody, glabrous, resinous (especially when young), opening elastically from the apex, obliquely to longitudinally nerved with minor anastomosing nerves, margins and partitions between seeds prominent, the apex hooked. Seeds 2-10, ob¬ liquely arranged in legume, ellipsoid or oblongoid (often irregularly shaped), (2.6-)3.0-3.9 mm long, (l.l-)l.3-2.1 mm wide, brown; pleurogram open, with a pale halo; areole slightly darker brown than rest of the seed; funicle-aril narrowly turbinate. Flowering January, March-April, July. Fruiting January, March-April, July-August. Figure 3f-j. Tindale & Kodela, Acacia 59 Distribution: Occurs in north-western Western Australia and Kakadu National Park, Northern Territory. Figure 2. Habitat: Usually in shrubland or open eucalypt savannah on rocky or stony plateaux and hill slopes. Etymology: The epithet refers to the fine, narrow phyllodes of this species. Notes: A. delicatuln is closely allied to A. subtemata F. Muell., which occurs in drier areas further south than the former (between c. 14°20'S and 16 17'S) in the Northern Territory near Borroloola, Tanumbirini and Willeroo. Another closely allied species A. manipula Cowan & Maslin ms., from the Kimberley area, Western Australia, differs from the former species in having less angular branchlets without prominent, minutely crenulated, resinous ridges and has longer phyllodes to 23 mm long. We have only seen one specimen of A. manipula ms., i.e. 9 miles [14.5 km] NE of Tablelands Home¬ stead, Kimberleys, M. Lazarides 6398. These species are members of the A. stigmatophylla group, which connects the Juli- florae with the Plurinerves (Tindale 1980). They differ from the other species listed in that their phyllodes are usually in groups of 2-6. In A. delicatula, A. subtemata and A. manipula ms. there is often a bulbous, yellow or brown cap on top of the ovary. Selected specimens: Northern Territory: Darwin and Gulf District: Kakadu, c. 2 km S East Al¬ ligator Ranger Stn, 12°25'S, 132°59'E, Naske, Aug 1987 (DNA 37225); near East Alligator River Ranger Station, Kakadu National Park, 12°29'S, 132°56'E, Russell-Smith 936, 23 Jan 1984 (CANB, DNA, PERTH); Jabiluka Outlier, East of Ja Ja, Ic. 12°30'S, 132°55'E], Waterhouse & Sanderson, 30 Mar 1980 (DNA, NSW, UNSW 9618); U.D.P. Falls, 7 miles [11.2 km| NW of El Sharana, |13°25'S, 132°25'E], Marlensz AE560, 24 Jan 1973 (BR1, CANB, DNA, NT); 13 miles 121 km] E of El Sharana Mine, 13°31'S, 132°42'E, Lazarides 7971, 2 Mar 1973 (CANB, NSW, PERTH). Western Australia: Fitzgerald: Gibb River - El Questro road, Karungi [Karunjie] Station turn-off, c. 130 km SW of Wyndham, |16°16'S, 127°12’E], Beauglehole 51489,28 May 1976 (BRI, PERTH); 50 metres E of turnoff to Pentecost Downs (Karunjie), Gibb River Road, Keith 225 & Pellow, 7 Jul 1986 (NSW, SYD). Key to A. delicatula and A. cataractae and close allies 1 Phyllodes usually in clusters of 2-6, cultrate to filiform, or sometimes ± narrow- oblanceolate, 4-18 mm long, 0.2-0.85 mm wide, nerves inconspicuous. 2 Phyllodes linear to filiform, (0.2-)0.3-0.4(-0.5) mm wide. Capitula 4.0-6.5 mm in diam. Calyx 0.6-1.0 mm long, dissected by 1/2-3/4, the sepals with ± subulate or acuminate apices. Corolla 1.3—1.75 mm long, the petals with midrib only ... A. delicatida 2* Phyllodes cultrate to linear or sometimes ± narrow-oblanceolate, (0.4-)0.5-0.8 (-0.85) mm wide. Capitula (5.0-)6.5-8.5 mm in diam. Calyx (0.9—)1.1—1.2(—1.4) mm long, dissected c. 1/2, the sepals ± spathulate with broadly rounded apices. Corolla 1.7-2.3 mm long, the petals striated longitudinally.A. subtemata 1* Phyllodes borne singly, oblanceolate to narrow-oblanceolate, or narrow-elliptical to very narrow-elliptical, 2.5-10.5 cm long, 6-23 mm wide, with several prominent longitudinal nerves. 3 Phyllodes with 1 of the 3 prominent longitudinal nerves usually confluent with the lower margin. Calyx 0.75-1.0 mm long, dissected by 2/3 or to the base. Petals with faint midrib.A. cataractae 3* Phyllodes with 3 prominent longitudinal nerves reaching the base. Calyx 0.5-0.75 mm long, cupular, dissected by 1/8-1/5. Petals with prominent midrib.A. stigmatophylla 60 Telopea Vol. 5(1): 1992 Figure 3. A. cntamctae. a, habit study with spicate inflorescences; b, upper portion of phyllode; c, habit study with legumes; d, inside of legume; e, seed (a,c. Brock 94; b,d,e, Menkhorst 297). A. delicatula: i, habit study with young capitula; g, phyllode; h, inside of legume; i, outside of legume; j, seed (f,g, Russell-Smith 936; h-j, Puttock & Waterhouse UNSW10162). a,c,f,h,i, scale bar = 1 cm; b,d,e,g,j, scale bar = 5 mm. Tindale & Kodela, Acacia 61 Sect. Juliflorae (Benth.) Maiden & Betche 4. Acacia gracilenta Tind. et Kodela, sp. nov. Acacia gracilenta: A. linarioidi Benth. affinis, sed phyllodiis late dispositis, non rigide erectis, 2.7-10.2 cm longis et 1.4-6.5 mm latis, stipulis basi 0.3-0.6 mm latis, ramulis, pedunculis et inflorescentiarum axibus glabris vel fere glabris et ramulis minus angu- laribus statim diagnoscenda. Type: Northern Territory: Arnhem Land, Upper East Alligator R., 12°50'S, 133°20'E, /. Russell-Smith 5270 & D. Lucas, 22 Apr 1988; holo DNA 36422; iso BR1, NSW 235962. Shrub to 3 m high, often spindly, spreading from a single stem close to the ground (e.g. from c. 15 cm); branches, branchlets and foliage resinous; bark greyish or light brown, ± smooth. Branchlets terete, finely striate, pale green and usually mottled with light brown, glabrous or sometimes with sparsely scattered, subappressed, minute, hyaline hairs, lenticels prominent. New shoots and young foliage greenish brown to red- brown, the margins of the phyllodes with appressed transparent hairs. Phyllodes borne singly or occasionally in pairs, linear or sometimes ± very narrow-elliptical, tapering gradually and equally from the centre or sometimes widest c. 2/3 from the base, straight or slightly curved, (2.7—)4.0—6.0(—10.2) cm long, 1.4-5.0(-6.5) mm wide, 7-30(- 45) times as long as wide, bright green, flat, herbaceous, glabrous or with appressed, opaque to transparent hairs to 0.6 mm long on the margin, the stomates prominent, the margins ± nerve-like; main nerves longitudinal, arising from the base of the phyllode; midnerve prominent, usually with 1 semi-prominent nerve either side, (2-)3-6(-7) nerves per 1 mm of phyllode width, sparsely anastomosing; apices acute to obtuse, often slightly constricted, mucro straight to oblique, red-brown to orange- brown, 0.2-0.8 mm long, an inconspicuous gland to 0.2 mm in diam. just below the apex; an inconspicuous gland to 6 mm above the pulvinus, often slightly indented in the upper margin, broad-elliptical to elliptical or oblong, 0.3-0.6 mm long, 0.2-0.3 mm wide, glabrous, the lip usually fawn, the orifice elliptical to slit-like, usually darker; pulvinus 0.5-1.8 mm long, wrinkles mostly transverse and often folded, brown or orange-brown, glabrous, often resinous; stipules 2 either side of pulvinus, 0.5-1.2 mm long, 0.3-0.6 mm wide at base, deltate, glabrous, with midnerve. Inflorescences spicate, borne singly in the axils of the upper phyllodes, 20-55 mm long, (3.5-)4.0-6.5 mm wide, c. 101-107 flowers per spike, golden; buds broad-ovate to very broad-ovate; peduncles 13-26 mm long, finely striate, glabrous, often resinous; bracteoles orange- brown, glabrous, usually resinous, the claw 0.15-0.3 mm long, the lamina ± perpen¬ dicular to the claw, 0.25-0.55 mm long, ± narrowly deltate, sometimes dentate. Floiuers 5-merous; calyx membranous, inconspicuous, the sepals almost free, cultrate to linear, 0.2-0.3(-0.4) mm long, the apices obtuse or ± spathulate; corolla (0.9—)1.0-1.3(—1.5) mm long, dissected for 1 /3-1 /2 of the total length (often to the base in older flowers), the petals elliptical to broad-elliptical or narrow-obovate, 0.5-0.7 mm wide, with a dis¬ tinct midrib, glabrous, often resinous, the apex thickened, often incurved and sometimes cucullate; stamens with filaments to 2.8 mm long; ovary oblong-elliptical, subsessile, brown, glabrous or sometimes with a few scattered, ± appressed, hyaline hairs to 0.15 mm long; style ± eccentric, 1.5-3.0 mm long. Legumes linear, usually curved, constricted between the seeds, coriaceous, (2—)4—9(—12) cm long, 2.5-4.0 mm wide, brown; margins paler, ± prominent; surface ± flat, slightly raised over the seeds, with several longitudinal nerves and minor anastomosing nerves, glabrous, usually resin¬ ous. Seeds (1—)6—11 arranged longitudinally in the legume, ellipsoid to narrow-ellip¬ soid, 3.5^L3(-5.7) mm long, 1.6—1.9(—2.7) mm wide, very dark brown or red-black to black; pleurogram closed, a very narrow groove separating the areole from the rest of 62 Telopea Vol. 5(1): 1992 the seed, often with a shallow trough around the pleurogram; areole 1.6-2.0(-2.6) mm long, 0.4—0.55(—1.0) mm wide, flat or slightly depressed, ± the same colour as the rest of the seed, sometimes less shiny; fiinicle cream-coloured, filiform, expanded into a cap-like aril, folded c. 5 times beneath the seed. Flowering and fruiting April-May, August. Figure 4. Distribution: Northern Territory: Darwin & Gulf District: Arnhem Land, Kakadu National Park and Katherine Gorge National Park. Figure 2. Habitat: Occurs in sandy soils on dissected sandstone plateaux and in gorges; often on slopes near rivers and creeks, growing amongst shrubs and sometimes with spinifex in open eucalypt woodland or Allosyncarpia forest. Etymology: The epithet refers to the rather graceful canopy of this member of sect. luliflorae. Notes: A. gracillima Tind., which is restricted to the Kimberley region of W.A. espe¬ cially in the King Leopold Ranges, is frequently confused with A. linarioides, which is a member of the A. lysiophloia group (Tindale 1978). It can be easily distinguished from A. gracilenta by its dark red, very curly bark, i.e. 'Minni Ritchi', and long hairs on the legumes. A. linarioides Benth. (occurring in the N.T. north of 17°S and on islands in the Gulf of Carpentaria) has slightly more angled branchlets and is more hairy than A. gracilenta. Specimens examined: Northern Territory: Darwin & Gulf District: Twin Falls, Jim Jim Falls area, 13°18'S, 132°52'E, Fox 559, 17 Aug 1974 (DNA 11803); 20 km south-east of Twin Falls, 13°27'S, 132°54'E, Lazar ides 8962, 24 May 1980 (BRI, CANB, NSW 235981); Kakadu National Park, upper Birdie Creek area, 13°53'S, 132°57'E, Slee & Craven 2512,18 Apr 1990 (CANB, DNA?, NSW 235987); Second Spring, Seventeen Mile Valley, Katherine [Gorge] National Park, 14°06'S, 132°24'E, I indale 6038 & Dunlop, 8 July 1979 (CANB, K, NSW 235964, UNSW); Katherine Gorge National Park, 14°18'S, 132°28'E, King 117, 2 June 1982 (DNA 23304). Key to A. gracilenta and A. linarioides 1 Phyllodes ± well-spaced, not stiffly erect, (2.7-)4-6(-10.2) cm long, 1.4-5(-6.5) mm wide. Stipules 0.3-0.6 mm wide at base. Branchlets, peduncles and axes of the inflorescences glabrous or almost so. Legumes 2.5-4.0 mm wide.A. gracilenta 1 * Phyllodes numerous, usually crowded, rather stiffly erect, 1-4.3 cm long, 0.4-2 mm wide. Stipules 0.1—0.2(—0.3) mm wide at base. Branchlets, peduncles and axes of the inflorescences usually sparsely to densely clothed with hairs to 0.7 mm long. Legumes 1.0-3.5 mm wide. A. linarioides 5. Acacia brockii Tind. et Kodela, sp. nov. Arbor gracilis, ad 5 m altam, phyllodiis argenteogriseis. Ramuli lenticellis, pilis albis plus minusve vestitis. Phyllodia juvenilia resinosa. Phyllodia linearia, recta vel parum curvata, 8.5-25.6 cm longa, 1.4-2.75 mm lata, plana, plus minusve rigida, pilis albis, caducis, appressis; nervis principalibus longitudinalibus, non anastomosantibus; mucrone apicali obliquo, 0.9-2.5 mm longo, glandula modo supra pulvinum disposi- ta. Inflorescentiae spicatae, singulares vel binatim e phyllodiorum axillis ortae, 23-43 mm longae, 3.5-4.5 mm latae, flavidae. Bracteolae florum ciliatae, alabastra superan- tiae apicibus acuminatis vel subulatis. Flores quinquemeri; calyx 0.8-0.9 mm longus.