28 ART. 14— K. YENDO: 



innermost one, remain in the original state, cf. pi. 1. fig. 3. Cor. verœ 

 Japon. 



The unizonal and the multizonal genicula differ genetically. In 

 the following paragraphs we shall try to give some details of the 

 development of both. 



One of the youngest geniculum formed from the single zone of 

 the periclinal cell is illustrated by the writer in " Cor. verse Japon. 

 PI. 1. fig. 2. The figure shows a longitudinal section of a branched 

 frond of Amp. valonioides. The geniculum of the branch is much 

 younger than that of the axial stem. The genicular cells are hardly 

 lono-er than the ordinary vegetative cells, with the circuingenieular 

 cortex still remaining as such. The differentiation of the cellwall 

 has already taken place in the genicular cells, staining the genicular 

 portion proper in deep violet by Boemer's hematoxylin. The 

 geniculum is already free from the deposit of calcium, while the 

 extragenicular portion is calcified as in the remaining part. 



As a general rule, the sum of the extragenicular portions at both 

 ends of the genicular cells is nearly equal to the average length of the 

 periclinal cells of the articulus. In some species (Gheil. anceps and 

 Jania species) the zonal arrangement of the periclinal cells is much 

 disturbed. As a consequence, the extragenicular portions of the cells 

 are very variable in their length. Those cells which have a compara- 

 tively short extragenicular portion at one end have in almost all cases 

 a much longer portion at the other : — the sum of both portions being 

 nearly equal in each cell. 



Tins circumstance teaches us that a certain zone of the periclinal 

 cells is divided into two parts along a plane perpendicular to the long 

 axis of the cells. At the division plane the intercalary growth of the 

 cells takes place, stretching the zone lengthwise. The cells elongate, 

 without deposition of the calcareons substance, and with a new 



