APPENDIX I 



NOTES ON SOME OF THE COMMONEST SHORE ALGi?E 



The drawings of seaweeds (Figs. 20 and 21) inserted in 

 this appendix are intended as a rough-and-ready guide 

 for the benefit of the beginner and represent the species 

 to which reference has been most frequently made in the 

 text. The notes below refer to the most obvious features 

 by which they may be identified. For the distribution 

 of Fucoids reference should be made to Plate VIII. 



Fig. 20. No. I. Pelvetia canaliculata. Distinguished by 

 its narrow fronds, usually without distinct mid-rib. The 

 margins of the frond are thickened and incurved so as to 

 give a channelled appearance to one side of the frond. Hence 

 the name of " Channelled- wrack." Receptacles (or specialised 

 region bearing the reproductive organs) terminal, oblong 

 or lanceolate, either in pairs or deeply-forked, their surface 

 tubercular. Air-vessels absent. Colour : a pale yellowish- 

 olive. Habitat : extreme high-tide mark. 



No. 2. Halidrys siliquosa. Easily distinguished by the 

 character of the receptacles which roughly resemble the 

 " pods " of a typical cruciferous plant. No air-vessels. 

 Colour : greenish-olive to olive-brown. Habitat : in deep 

 pools between tide-marks, never exposed to the air. When 

 occurring in shallow pools is usually stunted. 



No. 3. Fucus vesiculosus (" Bladder- wrack "). Frond 

 flat, with a stout mid-rib and entire margin. Air-vessels 

 elliptical, mostly in opposite pairs along the frond. Recep- 

 tacles terminal, roundish ovate, oblong or lanceolate. 

 Colour : deep olive-green. Habitat : typically at about 

 half-tide mark in situations where it is left exposed to 

 the air. 



No. 4. Laminaria digitata ('* Tangle-weed "). Easily 

 recognised by its large size, long cylindrical stem expanding 



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