Cytological Studies 



on 



Porpliyra tenera KJELLM. I. 



By 



Mitsuharu Ishikawa. 



In 1896 JoFFE has published a cytological account on the fertili- 

 sation phenomena of Porphyra and Bangia (4), in which he, as the 

 first investigator, correctly described and figured the nucleus of 

 Porphyra. Several literature dealing with the ecology or life history 

 of Porphyra has been published, yet no figure perfectly illustrating 

 the nucleus has not been known except that of Joffe ; and concern- 

 ing the cytology, especially with regard to the nuclear phenomena of 

 the plant in question, no other paper than Joffe's is known, and 

 therefore no investigation was done with the modern methods of 

 technique. Thus our knowledge concerning the details of the cytolo- 

 gical structure of this lower member of Rhodophycese is far from 

 being complete. Having much economic value as food material, 

 Porphyra tenera (" asakusanori ") is cultivated from long ago on a 

 large .scale in several places of Japan, especially in Tokyo Bay, but 

 comparatively little is known of the details of the life cycle and 

 various ecological problems are left unsolved. Prof, Dr. K. Okamura 

 who has much interest on the study of Porphyra tenera has recently 

 been granted with a research-fund of the Department of Education 

 and has begun a study on this subject. I have been advised by him 

 to take up the subject from the cytological point of view. The 

 following is a brief account of a part of my results. The present 

 work was done under the direction of Prof. K. Okamura, to whom 

 I am much indebted and desire to express my sincere gratitude for his 

 valuable advices and many helpful suggestions. Thanks are also 

 due to Messrs. K. Onda and M. Higashi who kindly supplied me 

 with materials and helped me with several useful suggestions. 



