30 Dansk Botanisk Arkiv, Bd. 2. Nr. 6. 



pary in Bruguiera, in which plant the seedling also falls to the 

 ground together with the pericarp, while in Rhizophora the empty 

 pericarp remains on the mother plant. 



The floating power of the seedling makes it possible for it 

 to be carried away by the currents, and in this way the disper- 

 sal of the species is furthered. This is an interesting exception 

 to the ordinary rule that sea-grasses do not possess any spe- 

 cial adaptation for an effective dispersal of their seeds or fruits. 

 Another exception is seen in Posidonia auslralis (see p. 35), but 

 it is remarkable that these two species nevertheless have unusu- 

 ally restricted geographical areas of distribution. 



4. Diplanthera uninervis (Forsk.) Ascherson, 

 in Engler u. Prantl, Natiirl. Pflanzenfam., Nachtr. (1897) 37; in Das 

 Pflanzenreich, IV 11 (1907) 152; Zostera uninervis Forskål, Fl. ægypt. arab. 

 (1775) 159; Halodule äustralis Miquel, Fl. Nederland. Ind. III (1855) 227; 

 Diplänthera tridentalä Thouars; F. v. Muller, Sec. Census Austral. Plants I 

 (1889) 204 



This species, not previously recorded from West Australia, 

 was found sparingly cast ashore at Carnarvon (No. 261). 



The specimens collected were all sterile. They have an elon- 

 gated creeping rhizome and short-jointed upright leaf-bearing 

 branches, some of which are more or less transformed into youn- 

 ger long-jointed rhizome branches. The leaves are short (4 — 6 

 cm long) and moderately broad (varying from 0.5 to 1.5 mm). 

 The apex of the leaf-blade has generally three teeth, the marginal 

 ones being more pointed than the central, which, in the narrower 

 leaves, is not much developed, in some cases wholly wanting, 

 thus making the apex two-toothed. 



D. uninervis is widely distributed along the tropical coasts 

 of the Indo-Pacific region, extending from the Red Sea to Oce- 

 ania. As to Australia I have seen specimens of this species from 

 Rockingham Bay ("Dugong Plant") and Port Denison, Queens- 

 land, both (unnamed) in the National Herbarium of Victoria. 

 Probably it will be found in other places along the tropical 

 coasts of Australia 1 ; on the other hand it can hardly be expected 

 farther south than Carnarvon, the most southerly record hitherto 

 known. 



1 F. v. Müller (1. c, 1889) records it from "N. A.", but I have not suc- 

 ceeded in finding his source for this record, as his quotation, "Fragm. 

 Phytogr. Aust. VIII, 218", only says, that it should be sought for 

 along the tropical coasts of Australia. 



