Marine Algce of the Orkney Islands. 333 



211. Polysiphonia elongata (Huds.), Harv. 



On stones and shells in deep water. Perennial. Fruit in July 

 and August. Linga Sound ; Deer Sound ; Hey Sound, &c., 4 to 

 15 fathoms. Not uncommon. 



212. Polysiphonia simulans, Harv. 



On rocks in tide pools near low- water mark. Annual (1) Summer. 

 Skaill Bay, "West Mainland. Identified by Harvey. 



213. Polysiphonia fastigiata (Roth), Grev. 



Usually epiphytic on Ascophyllum nodosum. Left uncovered by 

 tlie tide, and exposed to the light for some hours daily. Perennial. 

 Fruit from June to September. 



214. Polysiphonia atro-rubescens (Dilhv.), Grev. 



On sand-covered rocks, also in pools near low-water mark, and 

 at a greater depth. All the year. Fruit in summer and autumn. 

 Calf Sound, 4 fathoms, coral bottom. The variety Agardhiana 

 also occurs. 



215. Polysiphonia nigrescens (Huds.), Harv. 



Common on rocks in pools between tide marks. Perennial, 

 but usual duration from March to October. Young shoots on 

 old plants generally appear in January. Fruit from June to 

 September. 



216. Polysiphonia parasitica (Huds.), Grev. 



On rocks, in shaded pools between tide marks; also epiphytic 

 on Laminaria Ityiierhorea. Always submerged. Annual. April 

 to October. Fruit in July and August. Mr PoUexfen has found 

 this plant in Kirkwall Bay, Skaill, Cairston Bay, and South 

 Ronaldshay. 



217. Polysiphonia byssoides (Good, and Wood.), Grev. 



In deep water. Annual. June to October. Fruit in July and 

 August. Papa-Westray ; Rousay ; Skaill Bay, West Mainland, 

 good ; Scapa Bay ; Caruess ; dredged off Crossiecrown, Kirkwall 

 Bay, b^ fathoms. 



BONNEMAISONIA, Ag. 



218. Bonnemaisonia asparagoides (AVood.), Ag. 



At quiet places in deep water. Annual. June to September. 

 Fruit in summer. Linga Sound ; Deer Sound ; Kirkwall Bay ; 

 and Skaill Bay, West Mainland. 



LATJRENCIA, Lamour. 



219. Laurencia pinnatifida (Gmel.), Lamour. 



On rocks in exposed places at low-water mark. Sometimes 

 epiphytic on Alg£e. All the year. Tetraspores in winter and 

 spring ; ceramidia in summer. 



