APPENDIX I 307 



of bushy growth characterised by being strongly impregnated 

 with Hme. Colour : dull purple, often fading to pure 

 white. Habitat : in pools, commonest towards low-tide 

 mark. Never exposed. 



No. 4. Ulva lactuca (" Sea-lettuce "). Fronds practi- 

 cally sessile and, when floated by water, inflated or cup-like, 

 with margins more or less cleft. Colour : yellowish-green. 

 Habitat : in pools above half- tide level. Another common 

 species is U. latissima, which is of a deeper green and has 

 a somewhat different frond. 



No. 5. Rhodymenia palmata. A common red seaweed 

 with flat, irregularly-branched, somewhat leathery fronds ; 

 well known to all coastal inhabitants, in Scotland at least, 

 as " Dulse." A very variable form. Habitat : ever5rwhere 

 between tide-marks where not too exposed except, say, the 

 upper third of the shore. 



No. 6. Chondrus crispus (" Carrageen Moss "), Another 

 common red seaweed, also of variable form. Stem elongate 

 (one or two inches), cylindrical at base but passing into a 

 flattened, dichotomously-branched frond. Habitat : the 

 lower third of the sea-shore, exposed and in pools. Colour : 

 dark reddish-brown fading to yellowish-green. 



No. 7. Porphyra laciniata (" Laver "). Frond broad and 

 membranous, irregularly cleft and with crisped margins. 

 Very common on some shores between tide-marks where 

 exposed to air, appearing at low-tide as filmy sheets coating 

 the rock or other weeds. Colour : variable, from pale 

 purplish-brown to dark purple. 



No. 8. Fucus platycarpus. Resembles F. vesiculosus, but 

 is distinguished therefrom by the absence of air-vessels and 

 also by its habitat which is higher up the shore, immedi- 

 ately below Pelvetia canaliculata (see Plate VIII). A further 

 difference between the two species is that in F. platycarpus, 

 male and female elements are produced in the same con- 

 ceptacle, while in F. vesiculosus they arise from different 

 conceptacles. 



