SIPHONACEiE. 
23 
latter genus, after the lime has been removed by acid, there remains a plexus of 
unicellular, branching filaments, filled with green endochrome, and essentially of the 
same structure and nature as those of Codium. In C. Opuntia these filaments are 
easily extracted, and may readily be pulled asunder ; in C. Tuna they adhere more 
closely and require to be carefully manipulated. The Halimedce , like the Caulerpoe , 
are confined to the warmer portions of the globe, and are particularly abundant on 
coral reefs, in both hemispheres. As many as thirteen species are described by authors, 
but several appear to have been founded on very insufficient data ; and probably they 
might be reduced by one-half. C. Opuntia is the most widely dispersed, being found 
abundantly in the tropical Atlantic and Pacific, and in the Mediterranean and Ped 
Seas. C. incrassata and C. Tuna occur in the Pacific as well as in the Atlantic, but 
are less universally dispersed than C. Opuntia. When seen in herbaria the species are 
frequently bleached white, but all are of a bright grass-green when growing. They 
are furnished with deeply descending, fibrous, much branched roots, whose capillary 
rootlets firmly grasp particles of sand, and with them form a solid ball, not easily 
broken asunder. 
1. Halimeda Opuntia , Lamour. ; frond very much branched, diffuse ; articulations 
reniform, flat, obscurely lobed or repando-crenate along the upper margin. Lamour. 
Exp. Meth.,p.Tj,t. ZOifig. 6. Dm. Cor. p. 90. Kutz. Phyc. Gen. t. 43, fig. 2. 
Kiitz. Sp. Alg. p. 504. Corallina Opuntia , Ellis and Sol. p. 110, t. 20, jig. b. Ellis , 
Cor. t. 25, a. (Tab. XL. B.) 
Hab. On rocks and in tide-pools, near high water mark, on the Florida Keys. 
Key West, W. H. H. : Prof. Tuomey. (v. v.) 
Root deeply descending, fibrous, densely compacted into a fusiform mass, 1-2 inches 
long. Stems very numerous from the crown of the root, weak, but supporting each 
other by their proximity, and thus forming very dense tufts, much and irregularly 
branched ; the branches spreading. Articulations, except one or two of the basal ones, 
which are oblong or cylindrical, broadly reni-form, the more normal ones twice as 
broad as their length, from to more than \ inch across, flat, rather thin, but much 
incrusted with calcareous matter, with a more or less evident or obsolete longitudinal 
ridge through the middle ; the superior margin somewhat repando-crenate or lobed. 
After the calcareous matter of the frond has been removed by acid, a spongy vegetable 
structure remains, made up of a plexus of slender, longitudinal, unicellular filaments, 
constricted at intervals, and at the constrictions emitting a pair of opposite, decom- 
pound, dichotomous, corymboso-fastigiate, horizontal ramelli, whose apices cohere 
together, and form a thin epidermal or peripheric stratum of cells, over the surface of 
the frond. When the surface is viewed vertically, the cohering tips of the ramelli 
appear like the areoli of a continuous membrane. The substance of the filaments is 
tough, and they are filled with green matter. No fructification has been observed. 
