C. H. Ostenfeld: Contributions to West Australian Botany. I. 



The Sea-Grasses of West Australia. 



By 

 C. H. Ostenfeld. 



General Remarks. 



The name "sea -gras ses" is here used to designate the few 

 Flowering Plants, which live in sea water and are unable to exist 

 in fresh or nearly fresh water. Thus I exclude by this definition 

 the brackish water genera, such as Zannichellia, Ruppia, Althenia 

 and Lepilaena and limit the group to the following genera : Halo- 

 phila, Enhalus and Thalassia of the Eijdrocharitaceæ ; Cymodocea, 

 Diplanthera (Halodule), Zostera, Phyllospadix and Posidonia of the 

 Potamogetonaceæ. The number of species of sea-grasses known 

 does not much exceed 30. Some of them have very wide areas 

 of distribution, others rather limited. 



As to Australia, about 13 species belonging to all the above 

 enumerated genera, Phyllospadix excepted, have been reported, 

 most of them from the eastern coasts of the continent, a few only 

 from the western side. 



During my visit to West Australia in 1914 I succeeded in 

 finding a couple of species new to the flora of that State, and in 

 making observations as regards the distribution and biology of 

 other species. An account of these observations forms the sub- 

 ject of the present paper, which also includes the earlier records 

 of sea-grasses along the West Australian coast. 



As early as in 1792 Labillardiére found a sterile sea-grass on 

 the West Australian coast near Cape Leeuwin and described it in 

 1806 under the name of Ruppia antarctica 1 . The same species 

 was later collected by Gaudichaud in 1818 at Sharks Bay and this 

 time male flowers were found and figured under the name of 

 Amphibolis zosterifolius Agardh 2 . 



1 Labillardiére, Nov. Holland. Plant, species, vol. II, p. 116, tab. 264, 

 1806. 



2 Gaudichaud, Voyage autour du Monde, Botanique, p. 35 et p. 161, 

 pi. 40, fig. 2. 1826. 



