i 29 



Frond from a usually cordate (rarely cuneate) base flabelliform, up to about 10 cm. wide, 

 proliferous from margin (proliferation sometimes abundant and imbricate), sometimes striate, 

 usuall) - distinctly zonate; colour greyish-green. Surface very minutely crustato-spiculose or granulose. 



Frond-filaments 30 — 60 u. in diameter, parallel, not contiguous, monostromatic at apex to 

 pluriseriate below, sparingly dichotomous, without evident supra-dichotomial constrictions, bearing 

 subsessile or shortly stalked 2 — 4-furcate, or long and simple, lateral appendages, arranged 

 in close, opposite or alternate or secund, semiverticils, or more laxly and irregularly distributed 

 around the filament. Lateral appendages acute, rather irregularly arranged in lower part of frond, 

 being often interruptedly distichous and secund, pedicellate and varying in length (30 ij. — 180 a); 

 in upper part of frond fairly regular in arrangement and size (40 — 90 a simple, 30 — 50 u. 

 coronate), originating" quite close up to the growing apices of the main filaments and speedily 

 attaining the normal shape. 



Stipes-filaments bearing lateral appendages 170 — 350 u long, consisting of a stout pedicel 

 2 — 4 times dichotomous above and terminating in acute prongs. [Figs. 16, 19, 23, 25^, 25c]. 



The description of ('. verticillosa published in the Journal of Botany (loc. cit.) now 

 somewhat expanded, was founded on two specimens collected at the island of St. Thomas in 

 the West Indies by the "Challeriger" Expedition and preserved in the British Museum (fig. 16). 

 More recently we have had the privilege of examining numerous examples of this species 

 collected by Dr. Börgesen in the Danish West Indies. A study of these has given us a 

 satisfactory confirmation of the validity of our species, and at the same time has shown us in 

 what details of structure it is liable to vary - - namely, the shape and arrangement of the 

 lateral appendages (fig. 23). This variability is indeed one of the remarkable features of the 

 present species. In the same plant and indeed on one and the same frond-filament, the lateral 

 appendages may vary from 2 — 4-furcate to simple, may be sessile or stalked, varying in length, 

 arranged in opposite, alternate or secund semiverticils, or irregularly scattered. It is not easy 

 to indicate any one precise characteristic of structure applicable to the whole frond, by which 

 the species may always be indisputably distinguished. The best guide is to be found in the 

 usually subverticillose arrangement of the acute lateral appendages in the upper, especially the 

 apical, part of the frond, and in the fact that these appendages are found to be strongly 

 developed quite close up to the grovving apices of the main filaments of the frond. 



The nearest allies are on the one hand U. Wilsoni, which resembles it in the verticillose 

 arrangement of its lateral appendag-es (fig. 67), but differs in the fact that these are always 

 obtuse and never acute; and on the other hand L r . spimtlosa which resembles it in a certain 

 degree by having acute-pointed, bi- to pluri-spinose, sessile or pedicellate lateral appendages, 

 but difters in the fact that these are secund (fig. 12), and almost always are monostichouslv 

 secund, and never in any way verticillate. Moreover the main filaments of the frond show 

 distinct supra-dichotomial constrictions in l\ spinulosa, and none in l \ verticillosa (fig. 23a). 



U. verticillosa is readily distinguished from U. Occidental is and U. argentea in having the 

 lateral appendages of its main filaments arranged in close subverticils, many-pronged and acute, 

 not capitate nor longly pedicellate. 



SIBOGA-VXPEDITIE I.XI1. 17 



