On the Periodical Liberation 

 of the Oospheres in Sargassum. 



{Preliminary Note.) 



By 



M. Tahara. 



In 1005 J. Lloyd Williams published an interesting paper" 

 on the periodical development of the sexual eells of Dictyota 

 dichotoma, growing on the coast of North Wales and Plymouth, 

 England. According to him, the oospheres and spermatozoids 

 of this alga are produced during its fruiting season in fortnight- 

 ly crops, bearing a definit relation to the tides. In the next 

 rear this phenomenon in Dictyota was reexamined by W. I). 

 Hoyt 2) at Beaufort, North Carolina. His observation however 

 differed remarkably from that of Williams ; the crops were 

 borne at monthly instead of fortnightly intervals. 



In the winter of 1008-1000 I had an opportunity to 

 spend a few weeks at the Misaki Marine Biological Station 

 of the Tokyo Imperial University. To m\ r surprise it happened 

 to me to find that Sargassum, one of the most common algae 

 of Japan, presents also a similiar periodicity in the liberation 

 ol the oospheres. Along the coast of Misaki there are about 

 ten species of Sargassutn'', of which Sargassum encrve Ac. was 

 the one with which I have chiefly concerned. This species is 

 very common in the vicinity and forms often a considerable 

 mass. Its fruiting season begins at the beginning of December 

 and continues probably till the cn<\ of April. 



On the L6 th. of December, the next day of my arrival at 

 Misaki, I met with some female individuals of this alga, that 



1 Wiiiiwi-. .). I.i. Mml. iii the Diclyoluccoe. Innal of Botany. 1906 



II". i \v. I >. Periodicity in the production of the sexual cells of Du 



dichotoma. Botanical Gazette. 1007. Vol. XI. III. 



\ i m>m, K. 'I'll, i ,.. Japan. Journal of Colli I 



Univ< t ii i . Vol. XXI. \ni. Ii i-\ 



