F. Børgesen: Rhodophyceæ of the Danish W. Indies. 



249 



Fucus gelatinosus Desfontaine, Flora Atlan- 

 tica, Tomus II, Paris Anno 6, p. 427. 



Laurencia obtusa var. crucifera Kütz. Tabulæ 

 Phycol., vol. XV, p. 20, tab. 55, figs, c — d. Hauck, 

 Meeresalgen, p. 206. 



The specimens (Figs. 238 — 239) referred 

 to tliis variety seem to agree very well 

 with the description of Desfontaine, and 

 furthermore with Hauck's variety cruci- 

 fera, to judge by his description and by 

 the figures of KtJTZiNG, quoted by him. 

 Amongst these figures my plants seem 

 most to resemble the plant which Küt- 

 ziNG has called L. cyanosperma (Tab. phycol. 

 vol. XV, pi. 58). Some of my plants also 

 had a no less striking similarily to a spe- 

 cimen in Maze and Schramm's algæ from 

 Guadeloupe called Laurencia intricata. 



The specimens found in exposed pla- 

 ces are slender and of very firm consi- 

 stency, while those from more sheltered 

 places are larger, broader and more gela- 

 tinous, forming in this way a transition 

 to the typical Laurencia obtusa. 



Upon a transverse section of the young 



parts of the thallus the 



central axis is in general 



easily distinguishable 



(Fig. 240); in one speci- 

 men from a very exposed 



place (my collection no. 



1491) the central axis was 



not visible, the whole 



tissue being composed, 



upon a transverse section, 



of roundish cells, largest 



in the middle, smaller 

 ^i!?' ^^?v/'T''fT^" outwards and all having rather thick walls. 



obtusa (Huds.) La- ° 



mour., var. gela- My specimens form mostly rather dense 



mtosa (Desf.) J. Ag. tufts, reaching a height of about 10 cm or more, 

 plant. (About 3:1). The thallus is slender, pyramidally cylindrical 



Fig. 238. Laurencia obtusa 



(Huds.)Lamour. var. gela- 



tinosa (Desf.) J. Ag. Part 



of a male plant. 



(About 3 : 1). 



