Lee Kong Chian Natural History Museum

Pyrrosia piloselloides (L.) M. G. Price, 1987

Kingdom:Plantae
Phylum/Division:Filicophyta
Class:Pteridopsida
Order:Polypodiales
Family:Polypodiaceae
Genus:Pyrrosia
Species:P. piloselloides
Common Names:Dragon's scale, sakat ribu-ribu, sisik-naga
Status:Common

Description

This is a small creeping fern with a thin, wiry rhizone that is covered with scales. Fronds are fleshy and dimorphic. The sterile fronds are oval, 1-7 x 1.2 cm, often adpressed to the substrate or linear of up to 15 cm long and hanging down. Fertile fronds are linear, petiolate and 4-16 x 0.3-1.5 cm. Both fronds are covered with stellate hairs. Sori are linear, running along the frond margin.

Read more about the Polypodiales order.
Read more about the Polypodiaceae family.

Distribution

Extends from north-eastern India throughout Southeast Asia.

Localities

Throughout Singapore.

Locality Map

General Biology

The fern grows on the bark of old trees, sometimes totally covering the trunk.

Life Cycle

The reproductive unit of the fern is the spore, contained inside the sporangium or spore case. These sporangia are usually found in clusters of different shapes and sizes on the under surface of the frond - in Pyrrosia piloselloides they are grouped along the margin of the fertile fronds. Within each sporangium are 64 microscopic spores. The sporangium is a specialised structure consisting of a swollen head of one cell thick. Transversely encircling this head is a single band of specialised cells, the annulus. These are dead cells, much larger than the other cells and with thick inner and thin outer walls. The annulus does not totally encircle the sporangium head. Starting at the junction with the stalk, it runs round the head to be interrupted by a mass of thin-walled cells, the stomium. The stomium is the weak point of the sporangium.

With the maturity of the sporangium, the annulus loses its water content as the surrounding air dries. The pressure exerted by the drying annulus causes it to straighten and this in turn results in the stomium giving way. The sporangium thus ruptures into two, the top half together with the spores is flung back. And just a suddenly it returns to its original position, causing the spores to be flung out. As spores are microscopic and light, they are dispersed by the air current.

When a spore lands on a moist surface, it absorbs water and sends out rhizoids that funcrion as roots. A green germ tube then develops from the spore, elongating and thickening to eventually form a tiny, flattened, heart-shaped, green prothallus. Not all ferns develop a heart-shaped prothallus but this species does. The prothallus develops sexual organs: round male antheridia containing sperms and flask-shaped, female archegonia with an egg each. Both sexual organs may develop on the same prothallus together or at different times. When a sperm manages to fertilise an egg, a young fern develops and sends out a simple green frond. Subsequent fronds will be more and more complex until the adult frond is formed.

Thus the fern has two phases in its life cycle. The spore develops into the gametophytic or sexual phase. The prothallus develops into the sporophytic or asexual phase. What we normally encounter is the sporophytic phase of the fern. You need to really search among damp areas to see the gametophyice phase.

Human Uses

The plant is used internally to treat cough, dysentery and gonorrhoea in native medicine. It is also chewed to ease the inflammation of gums.

References

de Winter, W. P. & V. B. Amoroso (eds.), 2003. Plant resources of South-East Asia No. 15(2). Cryptogams: Ferns and fern allies. Prosea Foundation, Borgor, Indonesia. 268 pp.

Holttum, R. E., 1966. A revised flora of Malaya. II Ferns of Malaya. Govt. Printing Office, Singapore (2nd ed.). 653 pp.

Parris, B. S., R. Khew, R. C. K. Chung, L. G. Saw & E. Soepadmo (eds.), 2010. Flora of Peninsular Malaysia. Series I: Ferns and Lycophytes. Vol. 1. Malayan Forest records No. 48. Forest Research Institute of Malaysia, Kepong. 249 pp.

Wee, Y. C., 2005. Ferns of the tropics. Times Editions-Marshall Cavendish, Singapore. 2nd ed. 190 pp.

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