April, 1919.] 



THE GERMINATION AND DEVELOPMENT. 



77 



is hence strictly sublittoral. The other two are httoral and 

 may be found mixed together. 



The flat reef chosen for the experiment ground is well 

 known to us for the rich growth of the two littoral Porphyras 

 from December to Maj'. During the season the greater part of 

 the reef-surface come within the Httoral formation. In summer 

 time, the tide level is much lower and the tidal fluctuation 

 much smaller than in winter and the Porphyra ground is left 

 wholly destitute of vegetation above the high- water marks. 

 Exact data of the seasonal difference of the tidal level were re- 

 quired before I started the building of the experiment ground of 

 Porphyra on the reef. 



There stands a tide-gauge at the Oshoro Cove, under the 

 care of the Land Surveying Bureau, Military Department. I 

 requested the authorities for the records obtained from the gauge. 

 Engineer M. Sugiyama who was in charge of the tide observa- 

 tion readily transmitted me the required data with the permis- 

 sion of publishing them. The following tables are prepared 

 from the records. Here I shall not miss the opportunity to 

 express my respectful thanks to the authorities for the kindness 

 extended and for the assistance rendered. 



Monthly Mean Levels of Floods and Ebbs Observed 

 During 1912-1916. 



N. B. The zero point 

 mean sea level at Oshoro. 



of the tide-gauge is at the height of 3.043 m. above the 



