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Telopea 9(2): 2001 
Platychorda B.G. Briggs & L.A.S. Johnson 
The recognition that Restio is a member of an African clade, which has no genera in 
common with the Australasian members of the family, led to the description of several 
genera (Briggs & Johnson 1998) to accommodate the diverse Australian species 
formerly named under Restio. Among these is Platychorda, restricted to the high 
rainfall region of the south of Western Australia. It is distinguished from other related 
genera by the six tepals, trilocular ovary and three style branches in the female 
flowers. The type species, P. applanata (Sprengel) B.G. Briggs & L.A.S. Johnson, occurs 
in seasonally inundated heaths and swamps from Augusta to Albany (Meney, Pate & 
Hickman 1999). In the same region, but known from only a single locality, is the only 
other species of the genus, which is now described. 
Platychorda rivalis B.G. Briggs & L.A.S. Johnson, sp. nov. 
A Platychorda applanata combinatione characterum sequentium distinguitur: vaginae 
culmorum et glumae pallidiores, non nitidae; spiculae masculinae acutae; spiculae 
femineae longiores, acutae, flore solitario. 
Type: Western Australia: Spearwood Creek, 8.3 km W of Sues Rd along Denny Rd, W 
of Nannup, 34°04'12"S 115°18’35"E, 24 Nov 1995, T.D. Macfarlane 2560 & A.R. Annels 5 
(holo PERTH; iso NSW). 
Caespitose, forming dense tussocks c. 20 cm across; base pilose with pale hairs; basal 
sheaths similar to culm sheaths, glabrous. Culms erect, straight, compressed, 
unbranched, 60-85 cm long, 1.3-2.2 mm wide, striate, glabrous, bright green; 
intemodes few, 8-25 cm long. Sheaths closely appressed, c. 7-15 mm long, glabrous, 
scarious-hyaline, brown; lamina 5-10 mm long, 2-2.5 mm broad, blunt, often 
weathering away. Inflorescence with short, slender, erect branches at several closely- 
spaced upper nodes; branches bearing several spikelets on filiform pedicels. Male 
spikelets narrow acute-ovoid, 4—5 mm long; glumes lanceolate, acute, dull tan-brown, 
glabrous or very shortly ciliate, to 4 mm long, lower glumes shorter. Female spikelets 
ovoid, 5—7 mm long, 2-3 mm wide, with 9—15 sterile lower glumes and 1 fertile upper 
glume; glumes similar to males; a few of the lowest glumes with a very short, blunt 
mucro. Male flowers: tepals 6, narrow-lanceolate, hyaline, glabrous; 2 outer tepals 
keeled, 3-3.5 mm long; 3rd outer tepal and inner tepals flat, slightly shorter; stamens 
3; filaments c. 1 mm long; anthers c. 1.3-1.8 mm long, not exerted. Female flowers: 
tepals 6, concave, glabrous, red-brown with broad hyaline margins, lanceolate, acute, 
3-5 mm long; staminodes 3; ovary trilocular; styles 3, shortly connate at the base. 
Capsule c. 1.2 mm long. Seed ellipsoid, c. 0.9 mm long, pale brown. (Fig. 4a-e). 
The epithet is from the Latin rivalis, pertaining to brooks or streams, referring to the 
habitat of the species. 
Distribution: known only from Spearwood Creek, a tributary of Blackwood River, 
east of Margaret River. Grows on moist peaty sand in sedgeland with tall shrubs; site 
constantly moist with considerable seepage through the substrate. 
P. rivalis is similar to P. applanata in culm anatomy, with culm chlorenchyma lacking 
pillar cells but interrupted by narrow, radially elongated sclerenchyma girders. The 
species are also similar in their seed surfaces, having an irregular pattern of 
subangular flat or slightly convex cells. P. rivalis is distinguished by the paler culm 
sheaths; glumes paler tan-brown, not glossy; male spikelets acute; female spikelets 
longer (5-7 mm long), acute, with only one flower. P. applanata has mostly tan-brown 
culm sheaths; glossy, dark brown glumes; male spikelets blunt; female spikelets ovoid 
to globular, blunt, with several flowers. 
