CERAMIACE^. 209 



I. MICROCLADIA. Grev. 



Frond compressed, decompound-dichotomous, or sub-pinnate, distichous, wdth an 

 articulated axial filament, corticated, opaque ; the cortical stratum formed internally 

 of large angular cells, externally of minute ones. Favellce sessile on the branches, 

 subtended by a few involucral ramuli, and containing, in a hyaline periderm, nume- 

 rous angular spores. Tetraspores immersed in the ultimate segments, formed out 

 of some of the superficial cells, triangularly divided. 



This genus was founded by Dr. Greville on the Fucus glandulosus of the Banksian 

 Herbarium, a little plant found along the European shores from the Coast of Ire- 

 land to the South of Spain, as well as in the Mediterranean Sea ; and which 

 possibly awaits discovery on the Atlantic shores of America. It closely resembles 

 Ceramhim rubrum in habit, but is evidently compressed, and much more opaque, 

 the cortical layer being formed of several rows of coloured cells. To this original 

 species I venture to add the two following from the Pacific Coast. 



1. MiCROCLADiA Coulteri ; frond inarticulate, compressed, distichous, decompound- 

 pinnate ; branches alternate, elongate, simple, bi-tri-pinnate ; pinnas and pinnula3 

 piano-compressed, without evident articulation, the ultimate ramuli broadly subu- 

 late, acute ; favellte sub-globose or bilobed, sub-tended by two or three short ramuli. 

 (Tab. XXXIIL A.) 



Hab. California, Dr. Coulter, (v. s. in Herb. T. C. D.) 



Frond six or eight inches long, half a line in diameter, compressed, becoming 

 more so upwards, slightly flexuous, undivided or slightly divided, set throughout, at 

 distances of half an inch, with lateral, undivided, viroate branches. These branches 

 are erecto-patent, pinnated with shorter branches or pinna;, half an inch to an inch 

 or more in length ; the lowest shortest, the rest successively longer to the middle 

 of the branch, and thence again shorter to the apex. The pinnce are piano-com- 

 pressed, about bi-pinnate, all the divisions alternate and erecto-patent, the ultimate 

 ramuli subulate and acute ; the apical lacinia; hooked inwards. No articulation is 

 externally visible in any part of the stem or ramuli when examined with a micro- 

 scope, but the internal articulated axial filament may be seen in some places with a 

 pocket lens. A section of one of the upper branches shows a large central tube, 

 surrounded by several series of polygonal cells ; the inner large, the rest succes- 

 sively smaller to the circumference, which is formed of minute cells. A cross sec- 

 tion of the base of the stem has a very different aspect : it exhibits a large central 

 tube, though considerably shrunk from that of the branches, surrounded by one or 

 more circles of large cells, sejjarated from the central tube and from each other by 



VOL. IV. — art. 5. E E 



