284 Marine Algce of Berwick-on-Tweed. 



CH^TOPTEKIS Ktz. 



Frons filiformis, ramosa, Kami, distiche pinnati, Pinnae 

 oppositae, Axis primarius, filis radicalibus dense implexis, 

 corticatus. Sporangia in ramulis fructiferis simplicibus, e strato 

 corticali axis primarii ortis, disposita. 



As I understand the genus Chcetopteris, it differs from Spha- 

 celaria in fructification,* since the sporangia are borne on short 

 special branches arising from the cortical layer of the main axis, 

 and not on the ultimate ramuli, and from Cladostephus by the 

 opposite, not whorled branches, and also in stem structure. f 



ChjEtopteris plumosa (Lyngb.) Ktz. 



Phyc. Gen., p. 293. — Sphacelaria plumosa, Lyngb., Hydr. 

 Dan., p. 103, t. 30, fig. c. 

 Fig. Chcetopteris plumosa, Ktz., Tab. Phyc. VI., t. 6, fig. 1 ; Areschoug, 

 Obs. Phyc, part hi., pi. 2, figs. 4 and 5 ; Tab. Nost. x., fig. 4-6. 

 Exsicc. Cladostephus plumosus, Holmes, Alg. Brit. Rar., no. 1. 

 Syn. Cladostephus distichus, Holmes, MSS. (Traill in Algae of Firth of 

 Forth, Proc. Royal Phys. Soc. Edinb. 1882.) 

 Cladostephus plumosus, Holmes, in Grevillea xi., p. 146. 

 Hub. In deep water beyond tide-marks occasionally washed ashore. 

 All the year. Fruit Winter. Very rare. Berwick Bay, Sharper 

 Head. 

 A rare and beautiful species, closely resembling Sphacelaria 

 plumigera in habit and general appearance. The fronds are 

 slender, two to four inches or more in length, irregularly 

 branched ; the base of the stem, as well as the branches being 

 naked for a short distance. The opposite pinnae are long and 

 closely set, usually arising from every joint, or when, as 

 occasionally happens, they are again plumose in their upper half 

 from every other joint. The sporangia are borne on short 



* Not in the cortication of the main branches, for in Sphacelaria 

 plumigera the rhizoidal filaments form a false cortex to the main axis. 



t The stem structure of Chcetopteris plumosa differs very little from that 

 of Sphacelaria plumigera, and is not identical with that of Cladostephus, 

 (vide plate x., figs. 2-7.) 



Mr Holmes was the first to point out that this species agreed with 

 Cladostephus in having fruit on minute special branches on the main axis ; 

 but, having only very imperfectly prepared sections of the stem at his 

 disposal, he was misled into thinking that the stem structure also was the 

 same as in that genus. Since seeing my more perfect sections, he quite 

 agrees with me that the genus Chcetopteris must be retained. 



