204 ALGM RHODOSPERMEA:. [Polysiphonia. 



50. Ptilota. Ag. Ptilota. 



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

 tween membranaceous and cartilaginous. Fruct. : minute, 

 aggregated capsules, surrounded by an involucre. Grev. — 

 Name ; 7ni\wTo$, 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. 307. — Fucus plumosas. Turn. Hist. t. 60. E. Bot. 

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

 jointed. Turn. I. c. 



Rocky shores. «. on the stalksof the larger Algae. 3. on the faces 

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

 full red or brownish colour, (in iS.) 



Tribe XIII. CERAMIE^E. 



Plants marine (except some species of TrentepohliaJ, 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 : 

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

 in proper receptacles or in distorted ramuli. 



51. Polysiphonia. Grev. Polysiphonia. 



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 ; 7ro\os, many, and oitywv, 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 Ihem in their places 

 of growth. 



