158 AEÏ. 12. K. YENDO. 



hypheal cells. The one extends almost always longitudinally 

 along the axial part of the frond and has a much thinner wall 

 than the other. It is rich in contents and has transverse septa 

 at intervals of certain distances. The other is much narrower than 

 the axial ones and extends in all directions, occasionally running 

 from one surface to the other, binding together the cortical 

 layers. It is destitute of a septum throughout its entire length 

 (PI. II, fig. G). 



By cutting a longitudinal (meridional) section of a terminal 

 segment of a well-grown plant through the depression at an 

 apical point, we find in the middle a notch, around which 

 numerous cells are aggregated without any obvious regularity. 

 The cortical layer at the external margin is much thinner, being 

 composed of 3-5- celled rows. The cells are smaller than those 

 of the cortical layer of other portions of the frond and are 

 radially elongated. The cells of the medullary portion are 

 exclusively septated and loosely arranged. They are all alike, 

 but those situated in the axial part are slightly larger in 

 diameter than the neighbouring ones. The former mostly run 

 longitudinally while the latter are directed obliquely outward 

 and ramify simultaneously to join with the cortical cells (PI. II, 

 iig. 5). 



The lower portions of the foliose type are terete or cylin- 

 drical, and have a structure similar to the complanated part in 

 essential characters. The cortical parts in these portions, 

 however, ai-e nearly twice as thick and the cells in a row are 

 18-20, or nearly twice as many as in the complanated part. The 

 hypheal cells are more compactly arranged, compressing one an- 

 other with nuich thicker cell-walls. 



The structure of the filiform frond is exactly similar to 



