Moreover in Pseudocodium the utricles firmly cohere together into a continuous pseudocortex, 

 and arise directly from the medullary filaments. Pseiidocodium was described and figured by 

 Madame Weber van Bosse in the Journal of the Linnean Society Bot. vol. XXXII. 1896 

 p. 209. And Codium we have briefly treated in an Appendix, confining our attention to an 

 enumeration of the species represented in the Siboga collections. 



The Flabellarieae are all destitute of calcification and consist of the following- o-enera - 

 Chlor odesmis, Avrainvillea, Rhipiliopsis, Flabellaria, Rhipilia, Cladocephalus, Rhipidodesmis, 

 Ca llipsygma , Bood kop sis. 



The Udoteae are all calcified and are as follows : — ■ Tydematiia, Pcnicillus, Rliipoce- 

 phalus, Udotea, Halimeda. 



Our attention in the present paper has been directed chiefly to the genera of the 

 Flabellarieae and Udoteae, which are much more nearly related to one another by external 

 habit or by peculiarities of structure than either group is to the Codieae. Some of these 

 peculiarities are as follows : — 



1). Dichotomial branching repeated either in one and the same plane, or in alternate 

 planes. Where the internodes (pseudo-articuli) are short and laterally contiguous in one plane 

 they combine to form a flabellule. Such simple flabellules are found uncalcified in Rhipidodesmis 

 caespitosa apparently (see p. 62) and in Callipsygma ; they are calcified in Udotea javensis, U. 

 papillosa, U. glaucescens, Tydemania and Rhipocephalus. Where the internodes (pseudo-articuli) 

 are short and divergent, and the dichotomies lie more or less in alternate planes, they are 

 either laxly interwoven into a cushion as in Boodlcopsis, a laxly intricated glomerulus as in 

 Tydemania expcditionis, or an intricated capitulum as in Penicillus pyriformis. The pseudo- 

 articuli are longer, little interwoven, and form a brush in other species of Penicillus-, they are 

 subparallel in the uncalcified tuft of Chlorodesmis comosa, and also in the complanate frond of 

 Udotea conglutinata and its allies where they are cemented together by a thin calcareous deposit. 



2). Trichotomial branching occurs in addition to dichotomial, in the basal part of 

 Chlorodesmis eomosa, in Boodleopsis, in Tydemania, in Penicillus Sibogae, in the capitulum of 

 P. dumetosus and in the flabellum of Udotea conglutinata and U. glaucescens. 



3). Verticillate branching occurs in Tydemania expeditionis, in Boodleopsis and 

 in the capitulum of both species of Rhipocephalus. 



4). Lateral outgrowths of the main filaments. These are of two sorts: — 



a). Papillae or short prominences. Papillae are numerous in Udotea papillosa. 

 They are borne on the front and back surfaces of the filaments and not on their sides. They 

 are not calcified at their apices, and probably serve either as osmotic channels between the 

 cytoplasm and the seawater, or as windows in the opaque calcareous sheath. In U. indica large 

 truncate or peltate papillaeform prominences cover the two surfaces of the very sparingly calcified 

 frond, that is to say, they are borne upon the exposed sttrface only of the external filaments, 

 and, fitting close together, form a primitive cortex of the frond. 



ö). True lateral outgrowths or stalked appendages. In U. palmetta the 

 frond is more calcified than in U. indica and is covered with appendages similarly situated as 

 in that species, but often bifurcate or even trifurcate and always pointed. The function of these 



