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



Special Part. 



Fam. 1. Potamogetonaceæ. 



This family furnishes five West Australian species of sea-grasses, 

 four of the tribe Cymodoceeæ and one of the tribe Posidonieæ. 



The Cymodoceeæ are the following: 



Cymodocea angustata n. sp. (subg. Phycagrostis) 



— isoetifolia Aschers, (subg. Phycoschoenus) 



— antarctica (Labill.) Endl. (subg. Amphibolis). 

 Diplanthera uninervis (Forsk.) Aschers. 



The tribe Posidonieæ has only one genus Posidonia, with 

 two species, one of which is Australian, viz.: 



Posidonia australis J. D. Hook. 



The three species of Cymodocea and Posidonia australis are 

 here dealt with at some length, while the Diplanthera material 

 does not show any essential point of interest. 



1. Cymodocea angustata nov. sp. 



Subgen. Phycagrostis. Rhizoma repens, foliorum cicatricibus 

 annulos apertos efjormantibus. Vaginæ foliorum longe obconicæ, 

 valde compressæ, 2 — 8 cm longæ, 4 — 5 (3 — 7) mm longæ, diametro 

 pluries longiores, distincte biauriculatæ, pallide purpur ascentes (in 

 sicco). Foliorum laminæ lineales, 9 — 13-nerviæ, 10 — 20, rarius 

 usque ad 60 on. longæ, 4 — 5 (3 — 6) mm latæ, superne sensim angu- 

 statæ et distincte serrulatæ, apice obtuso. Flos masculus ignotus. 

 Flos femineus præter stigmatum apices inclusus; carpella bina ovo- 

 idea; stylus curtus teres; stigmata bina, longissima, filiformia. Fruc- 

 tus (immaturus) compressus, suborbicularis vel ovali-orbicularis, 

 marginibus integerrimis. 



Differt a C.rotundata et C. nodosa præcipue foliis latioribus 

 distincte serrulatis; a C. serrulata præcipue foliis angustioribus, 

 longioribus et vaginis longis, pallide purpurascentibus ; ab omnibus 

 præcipue foliis superne angustatis. 



Hab. in mare ad Carnarvon Australiæ occidentalis. 



