4 M. Tahara. 



two or three days after the liberation of Sargasswn énerve occurs 

 almost always the liberation of Sargasswn Horneri. Tlie same 

 relation is given in my record of the previous year. 



The highest spring tides occurred on the 11th and 25tli of 

 January and on the 10th and 24th of Februar3^ The dates with 

 asterisk in the table correspond to the days next after the highest 

 spring tides. 



I have also observed such oogonium liberation in Sargassum 

 Kjellmanianum, Sargasswn tortil, and CystophjUiim sisymbrioides. In 

 these algae too, the successive liberations do not seem to show a 

 fixed relation to the highest spring tide; for example, in S. 

 Kjellmanianum the liberations took place on» the 7th, 15th and 23rd 

 of February and in Cyst, sisymbrioides on the 17th of February and 

 the ord and 20th of March. 



All these facts led me to the conclusion that the liberation of 

 oogonia in Sargasswn and CystophyUum takes place periodically and 

 simultaneously among individuals of the same species growing in 

 the same locality ; but the intervals between two successive libera- 

 tion vary in an irregular manner, without having at least any fixed 

 relation to the highest spring tide. Thus the liberation phe- 

 nomena in our plants are somewhat different from those in Dictyota 

 dichotonia^ the periodicity of which was studied first by Williams'-* 

 and recently by Hoyt"'-* and Lewis. ^^ Probably owing to differences 

 in local conditions, the result of the observations of these authors 

 do not agree in details, but all of them agree that the liberation 

 phenomena of this alga have a certain relation to the highest 

 spring tide. 



To ascertain how the liberation of oogonia proceeds under 

 artificial conditions, I kept some branches of S. Humeri and Cyst. 

 sisymbrioides in a glass vessel filled with sea- water. To prevent 

 contamination the culture Avater was renewed almost every day. 

 The liberation did not occur as in nature at all; but after about a 



1) Williams, Studies in the Dictyotaceae. Ann. Bot., XIX. 1905. 



2) Hott, Periodicity in the production of the sexual cells of Dictyota dichotom:i. Bot. 

 Gaz., XLIIL 1907. 



3) Lewis, Periodicity in Dictyota at Naples. Bot. Gaz. L. 1910. 



