STUI'V OF THE GENICULA OF COIiALLIX.K. 



31 



transverse septa in the periclinal cells. These septa begin to appear 

 first in the cells at the peripheral region (fig. 6). 



Tn the beginning each genicular cell has two or three septa at 

 nearly equal distances. As the process is carried on further, more 

 se;>ta are continuously formed between the old ones. At last the long 

 fibrous cells are divided into a number of col lenchy matous cells, with 

 a much thickened membrane and scanty room. The zonal arrange- 

 ment of the cells is much disturbed. 



The peripheral cells which are now globular from the septation 

 begin to form a secondary cortex. The cells continue to divide 

 tangent ially and the thickening of the wall increases further. The 

 consequence is a thick layer of cortex, overlapping the distal ends of 

 the articuli at both sides. The length of the geniculum at the axial 

 portion does not very much exceed that of a young geniculum. We 

 always find the large bandform genicula at the basal portions of the 

 fronds in those species such as Amp., dilatata, Amp. ephedrœa, Amp. 

 Boiverbankii, etc. The width of the genicula is often larger than the 

 length of the neighbouring articuli. This modification is due to the 

 peripheral part of the genicula extending to cover the distal ends of 

 the articuli. The accompanying figures J and K show the longitudinal 

 sections of the fronds of A mp. dilat a ta through the genicula. Fig. J 

 is a completed geniculum but without the secondary growth of the 



peripheral cells; fig. K. is a rather old geniculum 



with the peripheral part of the genicula overlapping 



the articuli at both ends. 



In these old genicula, the medually and the 



cortical portions are more or less distinguishable. 

 The former has the cells some what elongated and an obscure zonal 

 arrangement of the cells is to be seen. The latter has cells with nar- 

 row rooms, thickened wall, and arranged in radial rows. The 



A' 



