The Correlation in the Differentiation 

 of Sex in the Fern Prothallia. 



Isabiiro Nagai. 



Tlie differentiation of sex in the fern prothallia is influenced by the 

 external conditions in qualitative as well as quantitative manner. The 

 part played bj' the nutrition and lij^ht has been studied somewhat in 

 detail (Nagai : 1914, 1915). A similar investigation has been extended 

 to certain other spicies of ferns. Few points of interest concerning the 

 internal relation in the development of antheridia and archegonia are 

 presented in this paper. 



The spores of Blechnum nipponicum (Kunze) Mak. w^hich were 

 collected in the vicinit}^ of Omagari, Akita-Ken in the autumn of 1916, 

 were sown on 0.5 per cent and 0.25 per cent Knop's solution on May 

 16th of the next 3ear respectively. Four different cultures were provid- 

 ed, from each strength of nutrient solution. They were placed near the 

 window of the laboratory except ones of each quadraples which w^ere 

 kept further apart from the window near at the corner of the 

 laboratory to receive weaker illuminiition. In the morning ample 

 diffused light was received and the maximum and minimum room tem- 

 peratures \vere recorded each. day. From time to time the prothallia 

 were taken at random from each culture and the number of antheridia 

 and archegonia were counted. The ret-iilts of observations are given in 

 the following tables. 



Table I.* Blechnum nipponicum. 



Observed Jul}' IStli (sixt}- days 

 after sowing) 0.25 per cent Knop's 

 solution. Grown under weak il- 

 lumination. 



* + anil — signs in the second column indicate the presence or absence of mer- 

 istem. F fur the filamentous and 11 for a more or less ^f^giilar heart shaped prothallium. 



