Enhalus and Thalassia have a loose membranous seed cover which slips off easily; a profuse growth of anchoring hairs is developed from the lower surface of the seed. The detailed morphological development of Halophila seedlings has been described for several species including H. spinulosa
(Birch, 1981); H. engelmanni (McMillan, 1987; Jewett-Smith and McMillan, 1990); H. decipiens (McMillan, 1988; McMillan and Soong, 1989; Kuo and Kirkman, 1995); H. tricostata (Kuo et al., 1993) and H. beccarii (Muta Harah et al., 1999,2000). The seedlings of all Halophila species display unusual early growth of 'hypocotylar hairs' or 'anchoring hairs' from the surface of the hypocotylar collar, which appear to anchor the seed before the emergence of the radicle (Fig. 16A and B). A similar phenomenon also occurs in fresh water monocotyle-donous seedlings (Kaul, 1978), in some aquatic dicotyledonous seedlings and in a few terrestrial plants (Arber, 1925).
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