Ferns have tissues for conducting water and food materials but do not develop seeds. The two most common species are ground-growing, semiaquatic species whilst the others are epiphytic (growing on trees) or climbers which are rarer in Singapore mangroves, e.g., Bird's nest fern (Asplenium nidus), Dragon's scales, (Pyrrosia piloselloides), Paku miding (Stenochiaena palustris).
The relative scarcity of ferns and bryophytes in the mangrove community is probably because part of their life cycle involves a gametophytic stage (gamete or sex cell-producing phase) where an algae-like thallus produces swimming antherozoids (male gametes) to move to the egg in another thallus, all of which are very susceptible to seawater.
Seawater, in osmotic terms, is 'physiologically dry' compared to the body fluids of plants and animals. This is why one cannot drink seawater to replenish water loss. When immersed in seawater, body tissues tend to lose rather than gain water. For the ferns, the stage most visible to us is the sporophytic stage (spore-producing phase) of the life-cycle.
Fact sheets on mangrove ferns:
Piai Raya Acrostichum aureum
Piai Lasu Acrostichum speciosum
From "A Guide to Mangroves of Singapore", Peter K. L. Ng and N. Sivasothi (editors)
Volume 1: The Ecosystem and Plant Diversity and Volume 2: Animal Diversity
Authors: Kelvin K. P. Lim, Dennis H. Murphy, T. Morgany, N. Sivasothi, Peter K. L. Ng,
B. C. Soong, Hugh T. W. Tan, K. S. Tan & T. K. Tan
BP Guide to Nature Series published by the Singapore Science Centre, sponsored by British Petroleum
© 2001 Raffles Museum of Biodiversity Research, The National University of Singapore & The Singapore Science Centre