THE MARINE BOTANIST. 245 



Section 2. — Diaphana. Smooth, the surface of 

 the articulation usually bare, or but partially 

 covered with coloured cellules, leaving a colour- 

 less space in the centre. 



CERAMIUM DECURRENS.— PARTIALLY 

 TRANSPARENT CERAMIUM. 



^^ Frond robust, gradually attenuated upwards, 

 dichotomous, with few lateral branchlets, the apices 

 hooked inwards, articulations partially coated with 

 coloured cellules, which extend from the dissepi- 

 ments at each end, but leave a coloiu*less, pellucid 

 space in the centre of the articulation; lowermost 

 articulations twice as long- as broad, upper very 

 short." Harv. Man., Ed. 2, p. 162. This species 

 differs from C. rubrum in having the centre of the 

 joint transparent, but the cells are continued 'part 

 way down the joint, a character which separates it 

 from C. diaphanum. Mrs. Griffiths does not con- 

 sider this a very satisfactory species. Grows on 



