162 THE BOTANICAL MAGAZINE. [Voi. xxxiir. No. 39.'. 



of archegonia in Blechnum as was alrcnd}' observed in Osmunda 

 (Prantl: 1881, CtOEBEL : 1887. Nagat : 1015). The archegonia were 

 formed exclusiveK' on the heart-shaped incristic prothnllia, no filament- 

 ous, or irrcgluarly shaped, ameristic prothalh'a are able to form arche- 

 gonia. However, the reverse may be true, the heart-sha];ed one ma}' 

 form antheridia alone and no archegonia. It was occasionaly observed 

 that the large, heart-shaped prothallia were covered with antheridia 

 but not a single archcgoniiim was found. It is evident that the de- 

 velopment of one sex inhibits that of t lie other. 



In the monoecious prothallia, the intern.-il relation or correclation 

 bet\veen the formation of antheridia and archegonia must be incomplete 

 or else independent. So if \ve measure the d^-gree of intcrdependince by 

 the group of individuals, a populatitni, by means of co-efficient of cor- 

 relation, we ma}' obtain the value from -1 to 0. It may be pointed out 

 here that the intensity of sex differentiation in a single prothalliuni and 

 a popxdation must be treated separatelv. When a bisexual population 

 is considered as a unit, diverse cases mav be included. Tlie pojmlaLion 

 may be composed wholly of dioecious individuals or may be composed 

 of monoecious individuals cxclusivel}', or else the mixture of them. This 

 point will be discussed later. 



Almost complete dioecism has been found in the cultures of uood- 

 wardia radicans (L) Sm., var. orientalis Sw.* and of Adiantum pedatum 

 L.t as in the case of Blechnum. 



Under normal condition, the prothallia of Blechnum spicant are 

 reported to be monoecious but the change in nutrition tends to jtroduce 

 dioecious prothallia ( Pellin : 1908). It is wtll known that the good 

 nutrition favors the formation of archegonia while the poor nutrition 

 that of antheridia. The response to the change in the nutrient con- 

 dition can be seen within a single prothalluni. 



The prothallia grown on 0.5 per cent solution were transferred to 

 1.0 per cent solution on thirty seventh day from the spores were 

 sown. Ninty da^'S later the prothallia were examined and they were 

 found to be dieocious except a small number of well grown individuals 

 which bore both antheridia and archegonia. In those prothallia ilie 

 formation of two sexual organ was distinctly localized corresponding 

 to the condition of growth of prothallia. Both regions were separated, 

 so it appeared as if two different archcgonia-bearing and antheridia 



* Tlie spores were collected .it Okitsu, Sliidziioka-ken. 

 t The spores were collected at Hiruguwa. .\kita-ken. 



