18 SIPHONACEJ]. 



branches, scarcely stipitate or subsessile, linear (in outline), 2-0 inches long, less than 

 half an inch wide, pectinato-pinnate from a sliort distance above the base to the extremity. 

 Rachis filiform, scarcely thicker than hog's bristle, closely set with pinnai. Pinnw 

 opposite, sometimes a little obliquely inserted, setaceous, 2-3 lines long, rarely straight, 

 generally more or less incurved or falcate, their apices sometimes very acute, ending in 

 a sharp mucro, sometimes bluntish. Substance when dry horny and semitranslucent. 

 Colour a deep and rather dark green, the tips of the pinnte often yellowish or orange. 



A native of the tropics generally, both of tlie eastern and western hemisphere ; occa- 

 sionally straggling into the warmer parts of the temperate zone. It varies much in the 

 diameter of the surculi, and somewhat in the length of the pinna;, but is easily recog- 

 nised by the closely pectinate fronds, which resemble small green feathers. The speci- 

 mens from Key West are peculiarly robust, and if compared with some slender varieties 

 from the Pacific, might pass for different. But at Vavau, in the Friendly Islands, where 

 this plant is common, I collected specimens both of the robust and slender form. 



Plate XXXVIII. C. Fig. 1. Caulerpa jihtnuiris, the tiatural size. Fig. 2, a pinna, 

 magnijied. 



4. Caulerpa Ashmeadii ; surculi naked, glabrous ; fronds erect, shortly stipitate, 

 distichously pectinato-pinnate ; rachis subcompressed ; pinnaj opposite (or suboblique), 

 erecto-patent, straight, linear, somewhat incrassated at the very obtuse extremity. 

 (Tab. XXXVIII. A.) 



Hab. Key West, rare. TF. H. //., Samuel Ashmead, Esq. (v. v.) 



Surcidi prostrate, distantly rooting, one or two lines in diameter, glabrous and 

 glossy, collapsing, and mostly channelled when dry. Fronds scattered, rising from the 

 upper side of the surculi, erect, each furnished with a stipes from half an inch to upwards 

 of an inch in length, and closely pectinato-pinnate throughout. Each frond, pinnie 

 included, is about an inch in breadth, and from four to six inches in length. The 

 pinnae are half a line in diameter, three-foiirths of an inch long, terete, and nearly linear, 

 but more or less thickened towards the extremity, which is very obtuse, without trace 

 of mucro or acumination. The substance when diy is horny and semi-transparent. 

 The colour, when recent, is grass green, but in drying it turns to olive. 



The roots, Mr. Ashmead remarks, penetrate so deeply, and fix themselves so firmly 

 in the hard sand, that it is with difiiculty obtained, except in fragments. I regard the 

 present as a distinctly marked new species, and have much pleasure in inscribing it to Mr. 

 Samuel Ashmead of Philadelphia, a gentleman who has already made some interesting 

 discoveries among the Alga; at Key West, and from whom many more may be expected. 

 It is a much larger and stronger growing plant than C. plumaris, and remarkable for 

 the very obtuse and almost club-shaped ends of the nearly straight pinnae. 



Plate XXXVIII. A. Fi[/. 1, Caulerpa As/uneadii, the natural size. Fit/ 2, a i)inna, 

 magnijied. 



