CHAPTER X 



THE LIFE-HISTORY OF THE MARINE 

 ANGIOSPERMS 



THE small group of Phanerogams inhabiting the sea 

 consists of about thirty species 1 belonging to two fami- 

 lies of that Cohort of Monocotyledons known as Helobieae. 

 The Hydrocharitaceae are represented by Halophila, Enhalus 

 and Thalassia, and the Potamogetonaceae by Zostera, Phyllo- 

 spadix, ^osidonia, Cymodocea and Halodule (Diplanthera). The 

 thorough way in which the marine Helobieae have identified 

 themselves with their environment, is shown by the fact that 

 Cymodocea antarctica was actually included by Agardh 2 in his 

 Species Algarum under the name of "AmphiboKs zoster ae- 

 folia"; injustice to this author it should, however, be mentioned 

 that he lays stress upon the uncertainty of its position "in 

 catena entium." Zostera marina, the Grass- wrack, often grows 

 among Seaweeds as if it were one of themselves ; in lagoons of 

 the Mediterranean coast it has been observed in association 

 with Enteromorpha, Codium tomentosum, Padina pavonia, Dictyota 

 dichotoma, and other Algae 3 , while in Danish waters it grows 

 in the midst of varied assemblages of brown, red and green 

 Seaweeds 4 . Zostera is even able to descend to considerable 

 depths in the sea; in the Baltic its occurrence at 1 1 metres from 

 the surface has been recorded 3 . A species of Phyllospadix (a 

 genus allied to Zostera} is noted for its power of withstanding 

 the violence of the waves; it grows on the Californian coast "in 

 the heaviest surf and on the most exposed ocean shores 5 ." 



Ascherson, whose work has done much to elucidate this 

 difficult group, pointed out about fifty years ago 6 that the 



1 Sauvageau, C. (iSgi 1 ). 2 Agardh, C. A. (1821). 



3 Flahault, C. in Kirchner, O von, Loew, E. and Schroter, C. 

 (1908, etc.). 4 Ostenfeld, C. H. (1908). 



5 Dudley, W. R. (1894). 6 Ascherson, P. (1867). 



