16 Fig. 5 FERNS <strong>and</strong> ALLIED PLANTS FDRV1 March 2011
FERNS <strong>and</strong> ALLIED PLANTS 17 MARSILEACEAE P.S. Short Aquatic or semiaquatic <strong>ferns</strong>; rhizome creeping. Fronds simple <strong>and</strong> filiform or with 2 or 4 leaflets at the apex <strong>of</strong> a stipe, with circinnate vernation, apparently modified leaves forming sporocarps. Sporocarps thick-walled, sessile or stalked, with several sori in each sporocarp <strong>and</strong> each sorus containing megasporangia <strong>and</strong> microsporangia. A family containing three genera (two in Australia) <strong>and</strong> about 70 species. Only Marsilea in the N.T. MARSILEA L. Rhizomes long-creeping. Fronds scattered along rhizome, the lamina <strong>of</strong> 2 pairs <strong>of</strong> opposite, closely spaced leaflets at the end <strong>of</strong> a long stipe, the whole having the appearance <strong>of</strong> a 4-leaved clover; leaflets glabrous or hairy, margins entire or crenate, veins radiating from the base. Sporocarps (or conceptacles) 2-valved, stalked, solitary or clustered at the base <strong>of</strong> or along the stipes, smooth or ribbed, glabrous or hairy, usually with 1 or 2 basal teeth which may be associated with the apex <strong>of</strong> the stalk. Sori exuded in a gelatinous mucilage. Nardoo. A cosmopolitan genus <strong>of</strong> about 70 species. Species delimitation is generally problematic within Marsilea. Jones noted that M. drummondii is highly polymorphic but it is evident that species are generally poorly delimited, supposed differences in features <strong>of</strong> the sporocarp being highly subjective. Jones recognised eight species for Australia, recording all for the N.T., but M. exarata was not recognised by Short (2003c) who also drew attention to a peculiar entity collected from Neutral Junction Station; the latter has since been formally named M. cryptocarpa. Only four species are here recognised for the D.R. In Marsilea, the hairs on the leaflets, stalks <strong>and</strong> sporocarps are not basally attached but are bifid. They have a very short arm <strong>and</strong> a much longer arm, so much so that they may appear to be simple, particularly when the long arm is spreading rather than appressed. Taxonomic references: Andrews (1990); Jones (1998a); Short (2000, 2003c). 1 Sporocarps lacking basal teeth; fresh leaflets with obvious colour b<strong>and</strong> ............ M. mutica 1: Sporocarps with 1 or 2 basal teeth; fresh leaflets lacking a colour b<strong>and</strong> ............. 2 2 Sporocarp with 1 tooth; leaflets mostly more than 3 times as long as wide ....... M. angustifolia 2: Sporocarp with 2 teeth; leaflets less than 3 times as long as wide ........................ 3 3 Sporocarps 2.5–3.5 mm long, unribbed, the upper tooth longer, narrower <strong>and</strong> more pointed than the lower; stalks shorter to nearly 2 times the length <strong>of</strong> the sporocarp ............................................................................................... M. crenata 3: Sporocarps 5.5–13 mm long, ribbed or unribbed, with the basal tooth obtuse <strong>and</strong> longer <strong>and</strong> broader than the upper, somewhat pointed, tooth; stalks usually 2 times or more the length <strong>of</strong> the sporocarp, rarely the length <strong>of</strong> the sporocarp ............................................................................................... M. drummondii M. angustifolia R. Br. Rhizome glabrous except for prominent tufts <strong>of</strong> orange-brown hairs on growing tips. Stipes 4– 22 cm long, slender, glabrous or sparsely hairy. Leaflets mostly narrowly elliptic or oblanceolate, 8–34 mm long, 2–9 mm wide, entire or with apices with irregular small teeth, glabrous or sparsely hairy. Sporocarp 6–7 mm long, densely hairy, basally with a single blunt tooth; stalk about the length or to c. 1.5 times the length <strong>of</strong> the sporocarp, rarely the apex somewhat tooth-like. Fertile <strong>plants</strong>: Apr. Fig. 6 (Rankin 2315). Endemic to Australia (W.A., N.T.) <strong>and</strong> widespread in the N.T. Grows in clay <strong>and</strong> s<strong>and</strong>y soils on the margins <strong>of</strong> seasonal swamps <strong>and</strong> streams. Rarely collected with sporocarps. FDRV1 March 2011