Etymology:
From the Latin pruinosus, covered with a waxy whitish bloom.
Illustration: Maconochie 1978, Hill 1996. Historical notes: Although strikingly distinctive and quite widespread, this species was only first recognised as recently as 1978 by Australian botanist John Maconochie. Distinguishing features: Distinguished by the narrow glabrous leaflets with strongly recurved margins, the long, slender microsporangiate cones, and the long megasporophylls with long sterile apices. Glaucous leaf waxes may be either present or absent, causing plants to be either blue or green in overall appearance. This is apparently genetically controlled, different populations being completely blue (eg. those at Lake Argyle and Bedford Downs), completely green (eg. those at Deception Range) or mixed (eg. those at Cycad Hill). A similar phenomenon occurs in C. furfuracea, in that case the green plants being very much less common and never occurring without the blue plants. Distribution and habitat: A widespread but sporadic species in the eastern and southern Kimberley region of Western Australia, occurring also in the Spirit Hills on Bullo River station in the Northern Territory. Found on mainly skeletal sandy soils on siliceous substrates, from metasandstones to granites. One occurrence in Western Australia is, however, on red Terra Rosa soil on limestone (near Tunnel Creek, in the Napier Range). Conservation status: Not considered to be at risk.
Description:
Stems arborescent, to 1.5(-2.5) m tall, 15-25(-35) cm diam. at narrowest point. Leaves bright green or blue, semiglossy or dull, 60-125 cm long, strongly keeled (opposing leaflets inserted at 45-90° on rachis), with 130-320 leaflets, with white tomentum shedding as leaf expands; terminated by paired leaflets or a spine 1-4 mm long. Petiole 8-23 cm long, glabrous or pubescent, spinescent for 50-100% of length. Basal leaflets gradually reducing to spines. Median leaflets simple, strongly discolorous, 110-170 mm long, 2.5-4 mm wide, inserted at 40-60° to rachis, decurrent for 2.5-4 mm, narrowed to 2-3 mm at base (to 80-100% of maximum width), 5-9 mm apart on rachis; median leaflets section slightly keeled; margins revolute; apex aristate, spinescent; midrib raised above, raised below (prominent). Cataphylls linear, soft, pilose, 70 mm long, persistent. Pollen cones fusiform, orange to brown, 35-45 cm long, 5-7 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, 20-30 mm long, 8-13 mm wide, fertile zone 12-18 mm long, sterile apex 9-14 mm long, deflexed, apical spine prominent, sharply upturned, 6-25 mm long. Megasporophylls 25-45 cm long, white-tomentose to grey-tomentose or brown-tomentose; ovules 2-6, glabrous; lamina lanceolate, 95-190 mm long, 18-40 mm wide, shallowly pectinate or regularly dentate, with 14-24 soft lateral spines 5-10 mm long, 2-3 mm wide, apical spine distinct from lateral spines, 10-45 mm long. Seeds flattened-ovoid, 32-36 mm long, 28-32 mm wide; sarcotesta orange-brown, strongly pruinose, 2-3 mm thick; fibrous layer absent; sclerotesta smooth. Spongy endocarp absent.
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