ip7 



exception {U . explanata) \ and are even, that is, equidistant above the dichotomy (see fig. 45) 

 in the West Indian species with the exception of U. occidentalis. What the cause of this 

 difference is, and why it should be associated with such a difference of geographical distribution, 

 we are unable to suggest. It appears to be a fundamental character, for it can be detected 

 at an early stage in the budding dichotomy at the apex of a frond filament. There is thus 

 a parallelism of species in the two regions, as the above table shews. 



As regards the above exceptions, it should be noted that U. occidentalis, though a 

 West Indian species, has uneven constrictions and is very closely allied to U. argentea, a 

 species with a wide distribution extending from the Red Sea to Queensland. It seems possible 

 that U. occidentalis may be an offshoot of U. argentea, modified by its West Indian environ- 

 ment, lts distribution is very limited. 



As to U. cxfilanata, an East Indian species with even constrictions (fig. 50), it has no 

 actual parallel in the West Indies, unless it be the cup-shaped U. cyatJiiformis\ and its presence 

 in the East Indies is perplexing (see p. 121). 



In U. verticillosa (fig. 23^7) and U. JVilsoni (fig. 67) the constrictions seem to be 

 masked, or rather suppressed, as a consequence of the abundant production of lateral appen- 

 dages. These originate so close to the apex of the filaments in these two species, as to inter- 

 fere with or prevent the normal formation of the supra-dichotomial constrictions. 



In U. fLabellum there seems no reason why the supra-dichotomial constrictions should 

 not exist, but the fact remains that they are absent in this species ; and further, that this 

 species is the only one which ia common to the Old and New worlds (see pp. 106, 133). As 

 stated on p. 133, we have failed to discover distinctions sufficiënt to separate the Eastern from 

 the Western representatives of this species. 



We have removed from the genus Udotea the following six species: U. pcltata J. Ag. 

 (= Rhipiliopsis, p. 45), U. Desfontainii Decaisne ancl U. minima Ernst which are placed in 

 Flabellaria (p. 46), U. amadclplia Mont. which is an Avraitwillea (p. 42), U. plumula Crouan 

 which is a synonym of Rhipocephalus Phocnix (p. 93), and U, sordida Mont. (= Avrainvillea 

 erecta, p. 29). 



Udotea Lamouroux 

 in Nouv. Buil. Sci. Soc. Philom. Paris III. 1S12. p. 186. 



Syn. Flabellaria Lamarck in Ann. Mus. Hist. Nat. XX. 1813. p. 294. 



Udotea Decaisne in Ann. Sci. Nat. Bot. 2^ sér. XVIII. 1842. p. 105 (pro parte). 



Flabellaria Chauvin Recherches... 1842. p. 123 (pro parte). 



Udotea J. G. Agardh Till Alg. Syst. V. 1887. p. 67 (pro parte). 



Udotea De Toni Syll. Alg. I. 1889. p. 505 (pro parte). 



Rhipidosiphon De Toni op. cit. p. 517. 



Udotea Wille in Engler und Prantl natürl. Pflanzenfam. I. Teil, 2. Abteil. 1890. p. 142, fig. 94 



(pro parte) 

 Rlupidosiplion Wille in op. cit. p. 144. 



Udotea Collins Green Alg. N. Amer. in Tufts College Studies II. 1909. p. 394. 

 Udotea Wille in Engler und Prantl natürl. Pflanzenfam. I. Teil, 2. Abteil. Nachtrage 19 10. 



p. 129 (pro parte). 



