208 



CERAMIACE^. v. 



Anthericlia have been found in several. They generally occupy the same position 

 on the frond as the tetraspores, and consist of innumerable minute, hyaline cellules 

 struno- ill moniliform filaments, radiating from a central point ; each of these tufts 

 of filaments being about the size of a tetraspore. 



Seventeen or eighteen genera of this Order are known. Of these the following 

 are represented on the North American Coasts. 



SYNOPSIS OF THE NORTH AMERICAN GENERA. 



Tribe 1. CERAMiEiE. Tetraspores (formed by a metamorphosis of some of the cor- 

 tical cellules) more or less sunk in the frond. 



I. MiCROCLADiA. Frond not obviously articulate. 



II. Centroceras. Frond articulated, corticated ; the cortical cells rectangular? 

 longitudinally seriated. 



III. Ceramum. Frond articulated, more or less corticated ; the cortical cells 

 roundish, irregularly distributed. 



Tribe 2. Callithamnie^. Tetraspores (formed by a metamorphosis of a whole 

 ramulus or of an articulation) external, sessile or pedicellate. 



IV. Ptilota. Frond corticated, decompound-pinnate. Favellce involucrate. 



V. Crouania. Frond gelatinous, articulated ; the stem and branches moniliform, 

 whorled with minute, densely set ramelli, among which the favellce are sunk. 



VI. Halurus. Frond cartilaginous, articulated ; branches whorled "with forked 

 ramelli. Favellce involucrate. 



VII. Griffithsia. Frond gelatino-membranaceous, articulate, dichotomous. Fa- 

 vellce involucrate. 



VIII. Callithamnion. Frond articulate, (the stem and branches occasionally sub- 

 opaque). Favellce naked. 



