210 CERAMIACE^. v. 



wide interstices filled with minute, filiform cellules. The stem does not readily re- 

 cover its form when moistened after having been dried, and this structure, attempted 

 to be shown is fig. 5, is not correctly given ; the specimen from which it was drawn 

 not having opened sufficiently. This difference in structure between the branches 

 and stem originates in causes exactly similar to those that operate in some Calli- 

 thamnia, in which the branches at first consist of a string of transparent-walled 

 cells, but afterwards have their walls filled from above with filaments, issuing from 

 the butts of the branches and gradually accumulating toward the base of the frond. 

 The favellce are formed on slightly shortened pinnules, and are roundish, subtended 

 by two or four subulate ramuli. Colour a purplish red. 



This is so similar to some varieties of Ceramium cancellatum that I had at first 

 referred it to that species ; but it is much more robust, more opaque, of a different 

 internal structure, and moreover the pinnas and pinnula;, which are lanceolate in 

 circumscription, are alternately rather than dichotomously compovmded. 



Plate XXXIII. A. Fig. 1. Microcladia Coulteri, the natural size. Fig. 2, a pinna; 

 Jig. 3, a pinnule vfith. favella ; Jig. 4, a longitudinal, and^^^. .5, a transverse section of 

 the base of the stem (not quite correct); the latter figures more or less highly 

 magnijied. 



2. Microcladia borealis, Rupr.; frond inarticulate, distichous, dichotomo-secund, 

 many times compounded ; branches arched, virgate, set along their upper sides 

 witli numerous, secund pectinato-dichotomous, twice or thrice secundly compounded 

 branchlets ; ultimate ramuli incurved, acute ; tetraspores in the ultimate ramuli, 

 irregularly scattered. Eupr. Alg. Ochotsk. p. 259- Microcladia scorpioides, Harv. MS. 

 in Herb. 



Hab. Una Nootka, Dr. Scolder ! Fort Vancouver, 1826, Garry ! Unalaschka, 

 Wosnessmski ! Golden Gate, California, Capt. Pike ! (v. s. in Herb. T. C. D.) 



Densely tufted. Fronds three to four inches long, as thick as hog's bristle, so 

 closely coated with periphei'ic cells that no articulation is visible in any part of the 

 frond without dissection. Internal structure as in the cenus. The branches and 

 all their subsequent divisions, though formed on a dichotomous type, appear from 

 the nearly constant regular suppression of one of the arms of the bifurcation to be 

 secund. The main branches are arched backwards, long and virgate, and closely 

 set with falcato-secund, distichous secondary branches, from half an inch to an inch 

 in length, and about a quarter inch apart. Each of these carries on its upper side 

 five or six secund ramuli, which are again once or twice compounded in a similar 

 manner. This order of ramification seems perfectly regular, without a trace of pro- 

 liferous growth. Tetraspores are abundantly scattered through the surface cells of 

 the ultimate ramuli in Capt. Pike's specimen. 



This appears to be a very distinctly characterised species and to belong to the 

 present genus, although it bears some external resemblance to Ceramium obsoletutn, 



