Acrostichum L.

Erect terrestrial or subaquatic ferns of medium to large size, mostly in brackish, sometimes in freshwater, swamps and marshes. Rhizome woody, short, stout, erect, dictyostelic with medullary strands, bearing broad thick scales attached by a broad base, often with aerenchymatous strut-roots. Fronds long stipitate, the stipes adaxially grooved, with a single U-shaped vascular strand, the lamina simply pinnate, the pinnae alternate, stalked, large, lanceolate or narrow-oblong, entire, thick-coriaceous, the apical pinnae similar to the lateral, a few reduced glandular pinnae that function in young fronds represented by short residual spines on the stipe, costa prominent, no main veins evident, venation oblique, closely anastomosing to form many series of irregular but ± uniform, narrow areoles, without included free veinlets. Sporangia acrostichoid, densely covering all or the apical half of the abaxial surface of the apical few pinnae, the fertile portions slightly contracted; exindusiate, paraphyses numerous, apically clavate or variously lobed (? = abortive sporangia), annulus longitudinal, interrupted, of 20-22 thickened cells. Spores trilete, pale, minutely tuberculate.

Mostly in coastal areas, especially mangrove. Sometimes classified as true mangrove (Chapman 1976; Maxwell 2002), or as associated mangrove. Most investigators like Troll (1933), Croft (1985), Tomlinson (1986), Kramer & McCarthy (1998), stated that A. aureum survives better inland, where A. speciosum is generally absent. On the contrary, Backer & Posthumus (1939) stated that A. speciosum can reach the altitude of about 900 m, meaning very much inland location, especially at mineral hotsprings. Some specimens previously identified as A. speciosum also come from a quite high altitude locality. Therefore, it is hard to differentiate A. aureum and A. speciosum by saline-freshwater preference.Some inland specimens collected far from the coastline, completely in freshwater, reflect the ability of A. aureum to tolerate the absence of salinity. Even cultivation in freshwater as in Kebun Raya Bogor is successful, reflecting that this species is totally able to live in freshwater. Some specimens were also being collected from inland in mineral springs, which may act as a substitute source of mineral and salt.The world record for altitude was by Kairo & Streimann NGF30938 from 1158 m (3800 ft) at Wau, Morobe, New Guinea. Occurrence of A. aureum from high altitude also recorded from some specimens as Bünnemeyer 8168 (Kerinci, Jambi, 850 m), Madulid PPI 18625 (Apulit, Palawan, 650 m), Bakhuizen v.d. Brink 6042 (Rawa Tjimandala, East Bogor, 500 m) and Rappart 217 (Air Poetih, Bengkulu, 450 m). One record by Collenette (1991) recorded the occurrence of A. aureum at 100 km inland in Saudi Arabia at the altitude of 823 m (2700 ft).