THE GENUS PHYLLOSPADIX. 



By WILLIAM RUSSEL DUDLEY. 



Phyllospadix belongs to a group of plants — the Sea Grasses, 

 remarkable in their morphological characters^ their habitat, 

 and the probable antiquity of the types constituting them. 

 The genera are few in number, variously reckoned from seven 

 to ten, embracing less than thirty known species, and includ- 

 ing all the flowering plants whose habitat is wholly marine. 

 The pollen, moreover, in all but three species, has the extra- 

 ordinary form of long, colorless, mycelioid filaments, a struct- 

 ure suited no doubt to processes of fertilization which must be 

 carried on usually under water. On the other hand, the or- 

 dinary granular pollen, adapted for transference through the 

 air, is practically universal among other Angiosperms. 



Two-thirds of the species mentioned form a section in the 

 Natural Order Potamogetonaceas, the other one-third are 

 grouped with a related order. The five marine genera in the 

 first-named order, all with filamentous pollen, are Zostera and 

 Phyllospadix forming a distinct tribe, Posidonia and the two 

 nearly related genera Cymodocea and Halodula. Zostera has 

 two widely distributed and three Australian species, Phyllos- 

 padix is peculiar to the Pacific coast of North America, known 

 from San Diego to British Columbia and probably beyond 

 these limits. Posidonia has one species in the Mediterranean 

 and one on Australian and Tasmanian shores. Cymodocea 

 has one species in the Mediterranean, one in the West Indies, 

 and five in the Indo-Pacific Oceans. Halodula has one species 

 in the West Indies, and one in the Indo-Pacific region. All 

 appear to be confined to a few fathoms below low-tide mark. 

 The small number of forms and their often remarkable isola- 

 tion suggest a long racial existence, marked by great vicissi- 

 tudes; and the fact that fossil remains, referable only to above- 

 named types, are found in the Tertiary and even in the upper 



