204 ALGJE RHODOSPERMEA:. \Poiy si 



50. PTILOTA. Ag. Ptilota. 



Frond compressed or flat, pectinato-pinnate, of a red colour, be- 

 tween membranaceous and cartilaginous. Fruct. : minute, 

 aggregated capsules, surrounded by an involucre. Grev. 

 Name; TrriXivrof, pinnated; from the delicately pinnated 

 fronds. 



1. P. plumosa, Ag. Feathered Ptilota. Frond compressed, 

 filiform, much branched ; the branches repeatedly pectinato- 

 pinnate ; pinnae and pinnulae exactly opposite ; the latter mi- 

 nute, subulate, and bearing the clustered capsules. Hook. Br. 

 Fl v. ii. p. 3Q7.Fuc2ts plumosus. Turn. Hist. t. 60. E. Bot. 

 .1308. /3. capillaris ; frond very narrow, flaccid; ramuli 

 jointed. Turn. I. c. 



Rocky shores, a. on the stalks of the larger Algae. &. on the faces 

 of perpendicular rocks. 6 18 inches long, many times pinnated, of a 

 full red or brownish colour, (in 0.) 



TRIBE XIII. CERAMIE^E. 



Plants marine (except some species of Trentepohlia ) ', of a red, 

 purple or reddish-brown, rarely brown colour, staining fresh 

 water with more or less of a red hue, of a cartilaginous or mem- 

 branaceous substance and cellular texture. Frond filamentous, 

 cylindrical or compressed, articulate. Fructification double : 

 1. Capsules, containing a mass of seeds ; 2. granules, contained 

 in proper receptacles or in distorted ramuli. 



51. POLYSIPHONIA. Grev. Polysiphoiiia. 



Frond filamentous, partially or generally articulate ; the articu- 

 lations longitudinally striate, with internal parallel tubes. 

 Fruit double : 1. ovate capsules, furnished with a terminal 

 pore, and containing pyriform seeds; 2. granules, immersed 

 in swollen ramuli. Name; TTO\OS, many, and cKfrwv, a tube ; 

 from the structure of the frond. The species of this genus 

 are numerous, and very difficult of determination; and I 

 freely confess, that I by no means fully understand all our 

 native ones. Many new ones will, doubtless, be discovered 

 on our shores by future observers, (for our rich coasts have 

 been but very imperfectly explored) ; and some, which I even 

 possess in my Herbarium, I have feared to introduce, until I 

 can have better opportunities of tracing them in their places 

 of growth. 



