Marine Algcv of the Orkney Islands. 317 



daily. Perennial. Fruit best in winter. An extremely broad 

 form occurs at the Bay of Damsay ; the var. latifolius of Turner. 

 I learn from ^Ir PoUexfen that Turner gave the name JatifoUu-i to 

 specimens 2 inches wide ; and that Greville speaks of one 2h inches 

 broad. One in Mr Pollexfen's possession from Damsay Bay, lately 

 mea.siired by Mr Batters, was found to be 5^ inches in breadth ! 



PELVETIA, Dene. 



101. Pelvetia canalicvilata (Linn. ), Dene et Thuret. {Fucuscanaliculatus. 



(Linn.) 



Common on rocks between half-tide level and high-water mark. 

 Always left uncovered by the tide, and exposed to the light for some 

 hours daily. Perennial. Fruit from June to September. 



ASCOPHYLLTJM:, Stackh. 



102. Ascophyllum nodosum (Linn. ), Le Jolis. {Fucus iwdosus, Linn.) 

 Common on rocks and boulders at about half-tide level. Peren- 

 nial. Fruit from December to September. 



103. Ascophyllum Mackaii (Turn.), Batters and Holmes. {Fucus 



Mad:aii, Turn.) 



Sea-shores, usually of land-locked bays. Perennial. April and 

 May. Mrs Molfat and Dr ^I'Bain both had Orkney specimens in 

 their collections, but the exact locality is unknown. 



HIMANTHALIA, Lyngb. 



104. Himanthalia lorea (Linn. ), Lyngb. 



On exposed rocks at about low-water mark. All the year. Fruit 

 in summer. Spores escape in August, j 



SARGASSUM, Ag. 

 104a. Sargassum. bacciferum (Turn.), Ag. 

 Sometimes cast ashore. 



104b. Sargassum vulgare, Ag. 



Sometimes cast ashore. 



Order VI.— DICTYOTE^. 



DICTYOTA, Lamour. 



105. Dictyota dichotoma (Huds.), Lamour. 



On rocks, and also epiphytic on Algae, in tide pools near low- 

 water mark, and at a greater depth. Annual. Summer. Found at 

 Broch, Kousay ; Wire Sound anchorage ; Howan Sound anchorage, 

 &c. ; variety ^ infricata, Grev., which variety has also been 

 dredged in Kirkwall Bav. 



