24 siphonacej:. 



Plate XL. B. Fig. 1. ITalimeda Opuntia, the natural size. Fig. 2, portion of the 

 branching, unicellular filaments of which the frond is composed ; magnified. 



2. Halimeda incrassata, Lamour. ; fronds solitary, erect, fruticose, somewhat flabelli- 

 form, much branched ; articulations thickened, the lowermost compresso-terete, qua- 

 drate ; the middle cuneate ; the upper (mostly) compressed, obscurely repando-crenate. 

 Lam. Exp. Meth. p. 25. Lam. Polyp, p. ^^1 . Dm. Cor. p. 91. KUtz. Sp. Alg. 

 p. 504. Corallina incrassata, Ell. and Sol. p. Ill, t. 20, d. — Var. /3, monilis ; all the 

 upper branches moniliform, composed of small, roundish, beadlike articulations. H. 

 monilis^ Lx. Dne.,Kiitz.,&c. Corallina monilis. Ell. and Sol. p. 1\0, t. 20, Fig. C. 



Hab. Florida Keys. Key "West, W. H. H. (chiefly var. ^.). (v. v.) 



Root a globose or oblong, bulblike, fibrous mass. Stems generally single, with a 

 short, undivided, compressed or subterete bole (or stipe) composed of two or more 

 incrassated and confluent articulations ; then expanding and divided into numerous 

 branches, which are repeatedly di-, tri-, or polychotomous at short intervals, spreading 

 generally in one place and thus forming a flabelliform frond. In the lower part of the 

 frond the articulations are very thick and almost confluent, a slender line merely defin- 

 ing the limits between each ; they are oblong or quadrate, and more or less cylindrical. 

 The middle articulations are more cuneate and less confluent ; and the upper ones, in 

 typical specimens, are still flatter and somewhat crenato-lobate. In the variety most 

 common at Key West, and which constitutes the H. monilis of authors, the upper 

 branches are slender and moniliform, composed of small, globose, or truncate, thick 

 articulations of variable size, and somewhat varying in form, the terminal ones on a 

 branch being frequently cuneate. The structure of the frond is similar to that of H. 

 Opuntia. 



Both varieties, as indicated above, are excellently figured by Ellis and Solander, and 

 by tKem and succeeding authors are kept as distinct species. Lamouroux indeed 

 observes {Pol. flex. p. 307) that the characters attributed to each are frequently con- 

 founded on the same specimen. This I find to be the case in specimens collected at 

 Key West, and I have, therefore, united the two forms under one specific name. 



3. Halimeda tridens, Lamour. ; frond solitary, erect, flabellately branched ; articu- 

 lations compressed, the lower ones quadrate or oblong ; the middle cuneate ; the upper 

 three lobed or tri-crenate. Lam. Exp. Meth. p. 27. Pol. Flex. p. 308. Dne. Cor. 

 p. 91. KUtz. Sp. Alg. p. 505. Corallina tridens, Ell. and Sol. p. 109- Tab- 20, 

 fig. a. (Tab. XLIV. C.) 



Hab. Key West, Prof. Tuomey. (v. s.) 



