133 



This species, the Corallina flabellum figured by Eu.is and Solander (loc. cit.) in i 786 

 enters largely into the early history of the genus Udotea (see p. 99). 



U. flabellum (fig. 26) is a very variable species as regards outward form, being either 

 simple and suborbicular with entire margin, or repeatedly and irregularly proliferous with a 

 more or less lobed margin. Any variation may occur between these extremes. An examination 

 of the internal structure however reveals at once the identity of the plant, for the lateral 

 appendages occur at irregular intervals (fig. 27) and are of unequal length, while the dense 

 and irregular subdivisions of their apices (fig. 27^) are so closely interlocked that it is difficult, 

 even after decalcification, to disentangle them without tearing them. A comparison between 

 the lateral appendages of U. flabellum and U. argentea shews that those of U. flabellum are 

 longer and more irregularly situated than those of U. argentea, and the apices of the lateral 

 appendages are quite different in their form, those of U. flabellum being dichotomouslv sub- 

 divided (fig. 27^), and more or less cymoidly compound (fig. 27a), while those of U. argentea 

 are either quite simple and pyriform (fig. 61), or once or twice divided, lobulate, inflated and 

 often embossed. 



U. flabellum is widely distributed in the tropical zone of both east and west hemispheres, 

 and, variable as it is in external form, it is at once recognisable in respect of its solid smooth- 

 looking superficial incrustation and of its internal structure, namely the spaced-out pluriseriate main 

 filaments with irregularly disposed lateral appendages of unequal length. The eastern plants 

 however, as compared with the western, sometimes shew a difference in the cymoid ramification 

 of the lateral appendages of the frond, the apices being truncato-capitate and not so dactyline 

 as in the majority of the western plants. The differences are however not sufficiently definite 

 or stable to enable us to separate the eastern plants as a distinct form. 



In the British Museum is a queer specimen collected by Dr. M. A. Howe in the 

 ponds of Walsingham, Bermuda, which have subterranean communication with the sea. It is 

 remarkable for its narrow elongate habit and linear proliferations ; probably clue to insufficiënt 

 illumination, and not to a modification of -the sea-water, since Dr. Howe's other specimen 

 from the same locality has comparatively broad proliferations. 



In the list of syhonomy for U. flabellum we have placed the name U. Halimeda 

 Kützing. This species was described by Kützixi; in his Species Algarum p. 503 and the 

 locality given as "Bahia (v. s. in coll. Binder)". The original plant described has been most 

 kindly lent to us for examination by Major Reixbold and shews the internal structure and 

 external form of U. flabellum. The plants from the Bahamas however, which are figured in 

 Kützing's Tab. Phyc. VIII. tab. 26. fig. 11 a and b, under the same name of U. Halimeda 

 are more markedly proliferous than the Bahia specimen [they resemble in outward form the 

 Siboga plants of U. argentea var. spumosa (see our fig. 15)]. It has not been possible to 

 tracé these Bahama plants. And hence their internal structure is unknown to us. 



U. flabellum occurs in all oceans within the tropical limits, and is remarkable as 

 being the only species of the Codiaceae (apart from a few species of Halimeda and Codium) 

 which is found in both hemispheres, East and West. 



