A STUDY OF THE GEXICULA. OF CORALLINE. 15 



of a geniculum are longer than those in the periphery. But there 

 occurs much fluctuation in the length, and the longitudinal section 

 of a geniculum always shows a zigzag appearance, cf. Cor. verœ Japon. 

 PI. III. tig. 3. 



In Amp. aberrans the genicular area changes abruptly into the 

 articular portion, and the boundaries between them are exceedingly 

 sharp. The boundaries are more or less convex toward the articular 

 parts at both ends of the geniculum. The majority of the Corallinœ 

 are of this respect, although the sharpness of the boundaries may 

 fluctuate in a slight degree (fig. 3). 



Amp. dilaiata, which shows special characters in various points, 

 here also gives us an aberrant type in this respect. The upper 

 boundary is a concave plane running into the geniculum and the 

 lower is a convex one running toward the lower articulus, with 

 special outgrowth at the central portion of both planes (fig. 5). 

 This character, however, is limited to the genicula of the upper and 

 middle portions of the fronds. The genicular cells of this plant 

 undergo further development and an old geniculum has an appearance 

 quite foreign to that of the younger ones. 



In Cheilosporum anceps, the zonal arrangement of the peri- 

 clinal cells is entirely disturbed. The cells are not straight but 

 undulating, and are connected with one another through the larire 

 lateral openings (fig. 4). In this respect it resembles the cellular 

 arrangement of the Jania, especially Cor. yenoshimensis. cf. Cor. verse 

 Japon. PI. III. fig. 3. 



Although the zonal arrangement of the periclinal cells is thus 

 irregular, the transition parts are regularly and sharply defined 



(fig- 4). 



In Cor. decussato-dichotoma and Cor. yenoshimensis the periclinal 

 cells are not undulated as in Cheil. anceps but the p?rforation on the 



