of which it has the stichidia and definite ramuli ; and Polysi- 

 phonia, which it resembles in habit. Some Polysiphonice, such 

 as P. versicolor and its allies, have similarly definite ramuli, but 

 their tetraspores are not contained in proper pods, but in the 

 ordinary branches : and this is the only essential distinction 

 between these genera. 



A. Fig. 1 . Polyzonia incisa, — the natural size. 2. Tip of a fertile branch, 

 with distichous, pectinate ramuli, two of which have ceramidia. 3. A ramulus 

 and ceramidium. 4. Spores. 5. Part of a ramulus and stichidium. 6. A 

 tetraspore : — the five latter figures more or less magnified. 



Plate XLIL B. 



POLYZONIA FLACCIDA, Haw. 



Polyzonia fiaccida ; primary surculus creeping; stems erect, arching, 

 simple or branched, very slender, flaccid ; ramuli pectinato-partite on 

 the upper edge, lacinise 5-6, filiform, acute, articulate, mono-di-si- 

 phonous ; stichidia arched, rostrate. 



P. fiaccida ; surculo repente ; caulibus erectis arcuatis simpUcibus v. vage ramosis 

 tenuissimis fiaccidis ; ramulis sursum pectinato-partitis, laciniis 5-6 filifor- 

 mibus acutis articulatis mono-di-siphoniis ; stichidiis arcuatis rostratis. 



Polyzonia fiaccida, Harv. in Trans. R. I. Acad. v. 22. p. 539 ; Alg. Exsic. 

 Austr. n. 146. 



Hab. Parasitical on small Algee. Fremantle and K. G. Sound, W. H. H. 

 Geogu. Distr. W. Australia. 



Descr. Very closely allied to P. incisa, but much more slender, of softer and 

 more flaccid substance, with longer, more numerous, and more attenuated 

 segments to the ramuli. In the specimens first seen, these ramuli are 

 monosiphonous ; but this character is not constant. The stichidia are very- 

 patent, and their apex is prolonged into a sort of beak. The colour is a 

 full crimson-red. 



This may perhaps be merely a very slender, deep-water variety 

 of the foregoing, or of P. Sonderi. When I first described it 

 I thought the ultimate segments were always monosiphonous, 

 but now find this to be a variable character. 



B. Pig. 1. Polyzoxia flaccida, — the natural size. 2. A ramulus with its 

 superposed stichidium. 3. A ramulus with monosiphonous lacinulse : — 

 both magnified. 



