V. RHODOMELACEiE. 17 



IV. ACANTHOPHORA. Lammr. 



Frond filiform, cartilaginous, irregularly decompound, opaque, coated with small, 

 polygonal, irregularly placed cellules ; axis articulated, polysiphonous. Ramuli 

 densely crowded on all sides of the branches, sliort, spinelike, acute. Conceptacks 

 urnshaped, perforate, borne on the ramuli, containing within a cellular pericarp a 

 tuft of pear-shaped spoi'es on simple funiculi radiating from a basal placenta. 

 Tetraspores tripartite, lodged in globose receptacles {stichidia) formed in swollen 

 ramuli. 



A small genus composed of a few tropical or subtropical species, the distinctive 

 characters of which are not well defined. They become very dark, often nearly 

 black, in drying, and are readily known by their spinelike ramuli. The natural 

 habit is nearly the same as in Akidium, but the stichidia have a difixjrent origin, 

 being here fonned out of the very substance of the ordinary ramuli, and not a 

 special axillary growth. 



1. AcANTHOPHORA TMerli, Lamour. ; irregularly pinnate or bi-pinnate, or not 

 much branched ; branches long, subsimple, tapering, beset throughout with quaqua- 

 versal, subulate ramuli, which are densely clothed with simple or trifid spines. 

 Lam. Ess. p. 44. Kiitz. Sp. Alg. p. 858. Fucus acanthophorus, Lamour. Diss. t. 30 <^' 

 31./. I. Turn. Hist. t. 32. A. inilitaris, Lam. A. muscoides, Grev. (Tab. XIV. A.) 



Hab. " Shores of North America," ZamoMrc»i<cr. Key West, W.H.H. (Xo. 4). Key 

 West and Conch Key, Prof. M. Tuorney (41, 42, 43). (v. v.) 



Fronds 3-6 inches long, half a line in diameter, alternately or irregularly 

 branched ; branches sometimes closely placed, sometimes distant, erecto-patent, 

 long, little divided, flexuous, sometimes having a few secondary branches above, 

 beset throughout at distances of a line apart with quaquaversal, very patent, short 

 ramuli. Ramuli one or two lines long, densely bristled with short, simple or 

 ti'ifid, broadly subulate, patent or reflexed spines. Conceptacles ui"n -shaped, with a 

 contracted orifice, seated on the sides or tip of the ramulus, and formed out of one 

 of its spines. A cross section of the frond shows five large primary cells surround- 

 ing a small central cavity, and a wide border of smaller irregularly angular cells, 

 gradually diminishing in size towards the periphery, which is fonned of very 

 minute cells. No outward appearance of articulation, or transverse striaa. Colour, 

 a dark, lurid purple, becoming brown or even black in drying. Substance carti- 

 laginous, firm. By pressure the plant may be made to adhere partially to paper in 

 drying. 



I regret that I had not noticed the conceptacles, which I find on one of Prof. 

 Tuomey's specimens, in time to introduce a figure of them into the plate. 



My specimens agree very fairly with the figure and description of Lamouroux 



D 



