630 University of California Publications in Botany [Vol.8 



Pelag-ophycus porra (Leman) Setchell 



Holdfast composed of whorls of dichotomously and later fasieu- 

 lately branched hapteres, the whole mass about 1.5 dm. diam. ; stipe 

 solid, terete and slender below, increasing slightly in diameter upward 

 for 6-7 m., merging abruptly into a swollen, hollow portion, the apo- 

 physis, about 80 cm. long, which is deeply constricted just below the 

 terminal bladder or pneumatocyst ; pneumatocyst spherical, 12-20 cm. 

 diam., filled with gas, giving rise on its summit to 2 solid branches, 

 1.3-1.6 m. long, decidedly flattened, each bearing about 5 short lateral 

 branches on the distal side ; the main and the lateral branches terminate 

 in blades which are 4-5.5 m. long, 20-45 cm. wide, with cuneate base, 

 borders loosely ruffled, more or less beset with small, spine-like pro- 

 jections, coarsely rugose, easily torn; sori scattered in irregularly 

 shaped areas. 



Growing in open waters, 10-15 fathoms, mostly attached to rocks. 

 From the vicinity of Point Conception, California, to some unknown 

 locality on the coast of Lower California (Mexico). 



Setchell, Nereocystis and Pelagophycus, in Bot. Gazette, vol. 45, 

 1908, pp. 129-134, The Elk Kelp, in Erythea, vol. 4, 1896a, pp. 179- 

 184, pi. 7, Kelps of the U. S. and Alaska, 1912a, p. 159 ; Collins, Holden 

 and Setchell, Phyc. Bor.-Amer. (Exsicc), no. CIX. Nereocystis 

 gigantea Aresehoug, in Bot. Not., 1876, p. 71. Pelagophycus giganteus 

 Areschoug, in Bot. Not., 1881, p. 49. Laminaria porra Leman, in 

 Diet. Sci. Nat., vol. 25, 1822, p. 189. 



Pelagophycus porra is quite limited in its distribution as noted 

 above. It has been known to the civilized world in a general way 

 since the days of the early Spanish navigators to the west coast of 

 North America. Although it is a plant which is normally anchored 

 relatively near the shore, it may become detached and, coming into 

 an ocean current, may float for many miles out to sea, remaining alive 

 for many months. The early navigators, on approaching the shores 

 of Mexico and California, were constantly on the lookout for this 

 floating seaweed, the presence of which was looked upon by them as 

 an unfailing sign of their near approach to land. Porra was one of 

 the names by which it was known, but the term also applied to both 

 Macrocystis and Nereocystis as well (cf. Setchell, 1908, for a complete 

 account of the early literature bearing on this alga). At present it is 

 generally known as Elk-kelp and is one of the kelps made use of in 

 large quantities during the recent war as a source of potash, etc. 



