100 



SEAWEEDS 



divisions of the cells of the growing point beneath 

 the apex. The characteristic mantle which forms 

 the secondary growth in thickness originates from 

 the basal cells of the lateral branches arising directly 

 below the growing point ; the cell-filaments so pro- 

 duced unite in parenchymatous fashion, and remain 

 closely adherent to the primary row and divide in 



FIG. 24.Detmarf*tia aculrata. a, longitudinal section showing mantle of 

 filaments ; b, transverse section. Highly magnified. 



several directions. The mantle ultimately consists 

 of two layers of tissue viz., a cortical layer consisting 

 of small cells engaged in assimilation, and an inner 

 layer of larger cells diminishing in size towards the 

 outside. In some cases these larger cells have 

 smaller ones intermixed with them. In the forma- 



