i9o8] 



YAMANOUCHI—APOGAMY IN NEPHRODIUM 



301 



established in a certain region of the superficial layer a group of 

 parallel cells. The increase of the superficial cell is remarkable in 

 apogamous prothallia. 

 In ordinary prothalHa, 

 if such a growth in size 

 ever occurs in a super- 

 ficial cell of the cushion 

 region^ it is an arche- 

 gonium initial; how- 

 ever, the archegonium 

 initial never attains 

 such conspicuous de- 

 velopment, surpassing 

 all the other superficial cells in that region. Moreover, the development 

 of the archegonium generally occurs after the cushion region has ex- 

 tended over a comparatively large area and attained some thickness. 

 On the other hand, the increase in size of the superficial cell in an 



Fig. 2.t-T\vo sections of normal prothallia, sho^-ing 

 different stages in the development of archegonia. 



a 



e 



b 



c 



Fig. 



CTadual 



ipogamous prothallium shoi^ing 

 roung cushion. 



arly stage and is associated 

 The accompanying figures 



will 



fig 



archegonium 



prothallia. Fig. 3 represents eight successive sections of the same 



