36 BRITISH CHAROPHYTA. 



internode (Fig. 10), and those of the ascending row 

 have a tendency to incline upward and those of the 

 descending row downward. 



Haberlandt suggests that the formation of the stem- 

 cortex is similar to that of some Alga3 and represents 

 a concrescence of closely-appressed lateral branches. 

 The cortical system can be best examined in the 

 younger growths, and the separate development of 

 each row of primary cells, with the lateral cells 

 belonging to it, can frequently be observed very clearly 

 in quite young branches in which they often grow 

 detached from the internodal cell. The cortical rows 

 follow the torsion of the stem, rendering it much more 

 conspicuous than is the case with ecorticate species. 



In most species of Chara the branch- 



ranc et ^^ ^ Q a j go cor ^ ca ^- e the cortex being 



cortex 



somewhat similar to that of the stem, 



but much simpler in character. At each of the 

 branchlet-nodes (except the highest, where there is 

 only one) two circles of single cortical cells are pro- 

 duced at the base of the bract-cells, one of which 

 grows upwards and the other downwards closely 

 appressed to the internodes, which they completely 

 cover, the cells being contiguous and the ascending 

 circle from the one internode meeting the descending 

 circle of that above it. Sometimes the cells forming 

 the cortex are of equal length, when their points of 

 meeting form an even ring ; in other cases they are of 

 more or less unequal length. In one of the British 

 species (C. canescens) the number of cells in the 

 ascending and descending circles equals that of the 

 bract-cells, and the cortex is described as haplostichous ; 

 in almost all the rest of the corticate Cliarse there are 

 two ascending and two descending cortical-cells to 



