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branches consist of a single longitudinal row of disc-shaped cells 

 and the plant makes its growth by the terminal as well as inter- 

 calary cell-divisions. The articulations are ^2-^/3 as shorter as the 

 diameter ; soon longitudinal partitions are formed near margins, 

 giving rise to the central and cortical cells. By further divisions 

 a cortical layer is produced covering the central cell. As the 

 branch grows in length the central cells increase in size, and as it 

 thickens it becomes unequal in thickness being bullato constricted 

 at short intervals. Cells of the primary articulation now become 

 almost globular or slightly depressed and those of the cortical layer 

 are either undivided or here and there divided into two. In this 

 stage the central cells are scarcely visible through the cortical 

 layer and the articulations are not externally constricted. As the 

 frond attains a thickness of some 300-400 , in diameter, the 

 central cells show a tendency to be destroyed and in a thicker 

 portion measuring 500-750 t l there is no remain of the central 

 cells leaving the interior of frond hollow. The fully formed cortical 

 layer consists of two layers of cells, of which the inner is larger 

 and roundish, while the outer is smaller and anticlinally a little 

 elongated. Cortical cells are not elongated in surface view, but 

 irregularly polygonal and closely disposed. They contain a distinct 

 neucleus and many roundish-angular chromatophores, while cells of 

 the inner layer are almost empty and colorless. On account of 

 the fragile substance the frond becomes, as the plant grows in 

 age, rather naked by dropping off of branchlets and apices of 

 branches become bluntish. 



Monospores (aplanospores) are formed in monosporangia 

 which are produced either directly from a cortical cell or from a cell 



