ULVACEiE. . 53 



I. PORPHYRA. Ag. 



Frond membranaceous, flat and leaf-like, purple. Fructification, dark purple gra- 

 nules (spores) arranged in fours, dispersed over the whole frond. 



The species of this genus are difficult to determine, and I am induced, in this place, 

 to unite the P. vulgaris and P. ladniata of authors, which I have elsewhere (Phyc. 

 Brit.) figured and described as distinct. They appear to me to run one into another ; 

 and if we contend for two species, with equal justice might we make half-a-dozen. Both 

 are indifferently used in England in the preparation of " marine saicce," or laver, which 

 is often brought to table as an accompaniment to roast meat. Kiitzing describes 

 sixteen species, several of which are probably reduceable to the following : — 



I. PoRPHYRA vulgaris, Ag. ; frond polymorphous, either undivided or cleft into 

 several broad segments ; sometimes peltate, fixed by a middle point. P. purpurea, and 

 P. laciniata, Ag. Sp. Alg. p. 19O — 191. P. vulgaris, Ag. Aufz. p. 18. Harv. 

 Phyc. Brit. #.211. P. laciniata, Harv. Phyc. Brit. t. 92. Wyatt. Alg. Damn. 

 No. 32. P. linearis, Grev. P. amethystea, Kutz. 



Hab. Rocks between tide marks. On the eastern shores from Charleston, South 

 Carolina, to the Arctic Regions. Western Coast, from California to Russian America 



(V.V.). 



Very variable in form in different localities and at different stages of growth. In an 

 early state it is either oblong or linear-lanceolate, with an evident though minute 

 stipes, and then it constitutes the P. linearis of Greville, which is found truest to its 

 type in the beginning of winter, in situations near high-water mark, where its vegeta- 

 tion is less vigorous. Later in the season the form usually called P. vulgaris, as 

 figured in Phyc. Brit. t. 211, will be found in the same locality, and also throughout 

 the whole space between tide marks. In this the frond is ovate or ovato-lanceolate, or 

 broadly lanceolate, much waved at the margin, and without obvious stipe, several inches 

 long and 2-3 inches wide. P. laciniata, Ag., which merely differs in having a deeply 

 lobed or divided lamina, grows mixed with the simple variety (P. vulgaris) ; and 

 specimens may easily be found which are intermediate in character. The state called 

 P. umbilicalis grows on exposed rocks, generally near low water mark, and looks more 

 like a different species than any of the other varieties. In it the frond is always short, 

 usually of a very dull colour, fixed by a point removed from the margin of the lamina, 

 and therefore somewhat peltate, with the upper side depressed or umbilicate in the 

 centre. This variety is rarely more than two or three inches in length. Other varieties 

 attain to 8 or 10 inches or more. 



The colour varies with the age and condition of the fronds. Often it is olivaceous 

 green, with little or no trace of purple ; but generally it is of a fine dark purple, 



