F. Børgesen: 



Rhodophyceæ of the Danish W. Indies. 



325 



part of the branch is monosiphonous except the basal segment, the 

 third one of the whole branch, which is polysiphonous ; in vigorous 

 plants the fourth and fifth segments, too, are polysiphonous. The 

 plant is quite without cortex. 



Falkenberg has pointed out that in the Mediterranean Sea he 

 has found two different forms namely a robust and very squarrose 



Fig. 326. Heterosiphonia Wurdemanni (Bail.) Falkenb. var. ty pica. 



a, part of the thallus with rhizoids developed from the summit of the 



ramuli. h, transverse section of the thallus. 



(a, about 180:1; b, about 300:1). 



form which is Hke the original specimens of Harvey from Key 

 West, and a more slender and not so squarrose form. Both forms 

 have been found in the West Indies (cp. Figs. 326 and 327). 



Fig. 326givesarepresentationof apartof the first-mentioned form. 

 As seen in the figure the ramification is very squarrose. The branches 

 are rigid, often curved with obtuse or acute angles and entangled 

 between each other. They are composed of rather short cells, in the 

 basal part about 60 \.i broad and about 70 \i long, tapering evenly 

 upwards and running out into acute, mostly curved apices ; towards 

 the top the cells at the same time become shorter. 



In the main axis the segments have 5 pericentral cells in my plants 

 (Fig. 3266) ; Falkenberg found 4 — 6 in his specimens. Of these cells the 

 three are lying on the upper dorsal side, the two on the ventral side. 



The other form (cp. Fig. 327) is much more slender and of a 



