6i 



peculiar, most probably unfavourable external conditions of life". He inclines to the view that 

 the peculiar scopulaeform habit of C. scoparius is due to desiccation of the tops of the plants 

 through exposure to sun and air during unusually low tides, foliowed by mechanical tearing 

 along the lines of least resistance, that is, parallel to the main filaments. 



It seems to us that there are three main objections to this ingenious theory. Firstly, 

 the plants occur in hundreds in the tidal pool described by Dr. Howe, and at depths of 

 2 — 10 dm. of water (low tide). Hence some at least of the plants would escape exposure 

 and desiccation. Vet Dr. Howe evidently did not find any of the plants to be flabellate. 

 Secondly, the solitary plant of C. scoparius found by Dr. Howe on the shores of New Provi- 

 dence is not recorded as occurring in a tidal pool. This additional record from another locality 

 is a strong argument in favour of C. scoparius representing a valid specific type. Thirdly, 

 the habit of C. scoparius is besom-shaped, and by no means suggests a compressed flabelli- 

 form origin. 



Our own view is that C. scoparius and C. luleo-fuscus are not conspecific but are 

 separate species by reason of difference of habit. 



The distribution of C. luteo-fttscus, so far as is known, is confined to the West Indies. 



3. Cladocephalus cxccuiriciis A. & E. S. Gepp 



in Trans. Linn. Soc. (Bot.) VII. 1908. p. 177, pi. 23, figs. 14—17; & op. cit. (Zool.) XII. 1909. 

 p. 387, pi. 48, figs. 14—17. 



Syn. Cladocephalus excentricus Wille in Engler und Prantl natürl. Pflanzenfam. I. Teil, 2. Abteil., 



Nachtrage 19 10, p. 129, fig. 66. 

 Hab. INDIC. Cargados Carajos, 30, 45, and 47 fathoms, J. Stanley GardinerX 



Plant bright green, solitary, up to 10 cm. high, quite distinct in habit from the other 

 two species of the genus. Stipes attached at base to calcareous substratum, simple, olivaceous, 

 up to 3 cm. long, terete, solid, 1 — 2 mm. thick. 



Frond unequally infundibuliformly peltate, widely expanded, at first rotundate, later 

 irregularly elliptic or lobate, up to 10 cm. broad, membranaceous, green, zonate. 



Medullary filaments radiating from the stipes, light green, 15 — 25 p. in diam., repeatedly 

 dichotomously branched ; branchlets pseudolateral, dichotomously and closely subdivided above, 

 tapering to about 5 — 10 u. 'm diam. at their apices ; ramelli interwoven to form the pseudo- 

 cortex. [Figs. 139, 140]. 



This species differs from the West Indian species in its peltate habit with its frond 

 concave above, and its stipes short, thin and unbranched (fig. 139). In this respect it resembles 

 Rhipilia leuaculosa, Rhipiliopsis pcltata, ancl Udotea cyathiformis. It is also distinguished from 

 the West Indian species of Cladocephalus by the closer branching of the medullary filaments 

 of its frond and by their much smaller size (fig. 140); they do not exceed 25 ij. in diam.; nor 

 do they exhibit the green or fulvous colour which characterises the frond-filaments of the 

 West Indian species. 



This is an East Indian species. It was not found within the area explored by the Siboga 



