324 Dansk Botanisk Arkiv. Bd. 3. Nr. 1. 



rally a short stalk composed of two cells. The stichidium is conical 

 in shape. At the upper end it often runs out in a rather long sterile 

 monosiphonous prolongation. The stichidia are about 300 |li long and 

 about 90 n broad. 



This plant was found in shallow water in sheltered places epi- 

 phytic upon Acanthophora: further in the open sea in deeper water 

 down to a depth of about 30 meters. It had tetrasporangia in the 

 month of March. 



St. Croix: Off Frederikssted. St. Thomas: Bovoni Lagoon. St. 

 Jan: off Cruz Bay. 



Geogr. Distrib.: West Indies, Atlantic coast of Europe and North 

 Africa, Mediterranean Sea. 



Heterosiphonia Mont. 



1. Heterosiphonia Wurdemanni (Bail.) Falkenberg. 



Falkenberg, P., Rhodom-elaceen, p. 638, pi. 16, fig. 11. 



Dasya Wurdemanni Bailey, Harvey, Nereis Bor. -Am., vol. II, p. 64, 

 tab. XV, C. KüTziNG, Tab. Phycol., vol. XIV., pi. 81. J. Agardh, Spec. 

 Alg., vol. II, p. Ill, p. 1191. Zanardini, Icon. Phycol. Adriat., vol. II, 

 pi. 53, A. 



Cfr. De Tom's remarks concerning Dasya rigidula (Kütz.) Ardiss. in 

 Sylloge Alg., vol. IV, sect. Ill, p. 1207. 



The essential difTerences between Heterosiphonia and Dasya 

 consist in (1) producing two or more segments to the sympodial 

 main axis in each branch-system in Heterosiphonia compared with 

 the one in Dasya; (2) placing the free summits of each branch- 

 system distichously alternate on both sides of the main axis, and (3) 

 the presence of a more or less pronounced dorsiventrality. 



Heterosiphonia Wurdemanni creeps upon larger algæ, stones and 

 shells and is fastened to the substratum by means of the rhizoid-like 

 ends or even discs often found in the summit of the branches (cp. 

 Figs. 326 a, 328 h). It forms small roundish spongy clumps two to 

 three cms high. Because of its mostly very squarrose ramification 

 it becomes easily entangled between other algæ. 



The main branch carries, besides the branch constituting the 

 continuation of the sympodium and placed upon the second segment 

 of the main branch, another branch issued from the fourth segment. 

 This branch is bent upwards, several times pseudodichotomically 

 ramified with divaricate and squarrose branches. Commonly the free 



