12 SIPHONACE/E. 



Sub-order II. CoDlEiE. Frond uni- or phiri-cellular. Cells filled with granular 

 endochrome (without internal fibrous network). 



* More or less coated ivith carbonate of lime. 



II. Halimeda. Frond branching, articulate ; the joints flattened. 



III. Udotea. Frond stipitate, fan-shaped, simi)le or cleft. 



** Destitute of carbonate of lime, soft and flaccid. 



IV. CoDlUM. Frond spongelike, of definite form, composed of closely interwoven, 

 irregularly branching filaments. 



V. Chlorodesmis. Frond stipitate (or subsessile), pencil-shaped, composed of dichoto- 



mous filaments, interwoven at base, and free in their upper portion. 



VI. Vaucheeia. Filaments numerous, tufted and somewhat matted at base, free 

 above, irregularly branched. 



VII. Bryopsis. Filaments free, tufted or solitary, pinnately branched. 



I. CAULERPA, Lamour. 



Frond consisting of prostrate surcidi, rooting from their lower surface, and throwing 

 up erect branches (or secondary fronds) of various shapes. Substance horny-membran- 

 ous, destitute of calcareous matter. Structure unicellular, the cell {ov frond) continri- 

 ous, strengthened internally by a spongy network of anastomosing filaments, and filled 

 Avith semi-fluid grumous matter. Fructification unknown. 



The genus Caulerpa was founded by Lamouroux in 1810, and referred by him to 

 his family of Ulvacefe, though with doubt ; for he seems to have thought the structure 

 of these plants so anomalous that he hesitates to pronounce them vegetables, notwith- 

 standing their strictly vegetable form, immobility, and green colour. He had not, 

 however, made himself master of their real structure, for he describes the frond as 

 " consisting of an epidermis, and a cellular tissue consisting of cells so small that it has 

 been impossible to determine their form" (Ess. p. 67j. Turner appears to have been 

 the first author who noticed the fibrous spongelike network which fills up the cavity of 

 the membranous frond. This he describes under his Fucus hyjmoides, but in terras 

 which show that he supposed this structure peculiar to that species. To Dr. Montague 

 we owe the first and best account of the structure of the Caulerpw. This able algologist, 

 in a paper read before the French Institute in 1837 and published in An. Sc. Nat. for 

 March, 1838, has given a full history of the genus, both as to its organization and what 

 he believed to be its fructification. To this memoir I refer the reader who wishes fin- 

 full information of all that was then known of these plants, and shall content myself in 

 this place with briefly describing their habit, structure, and geographical distribution. 



