MARINE ALGJB, OF BEAUFORT, N. C. 421 



Seven species, some of them grading into each other, throughout the world. 



KEY TO SPECIES. 



Frond entire or irregularly lobed or laciniate i. U. lactuca (p. 421). 



Frond divided into distinct segments 2. U.fasciata (p. 422). 



i. Ulva lactuca Linnaeus. 



Ulva lactuca, Linnaeus, 1753, vol. 2, p. 1163. 



Ulva latissima, Harvey, 1858, p. 59. 



Ulva lactuca var. lactuca, Farlow, 1882, p. 43. 



Ulva lactuca, De Toni, 1889, p. in. 



Ulva lactuca, Collins, 1909, p. 214, pi. 7, f. 75. 



SEA LETTUCE. / 



Frond very variable in shape, at first attached and generally of a lanceolate or ovate-lanceolate form ; 

 later of irregular shape and often detached and floating; the cells usually vertically elongate in cross 

 section, seen from the surface, irregularly angular, closely set; thickness of the frond very variable. 



In all seas. 



Beaufort, N. C. : Abundant on rocks and on other algae, Fort Macon and Shackleford jetties, through- 

 out the year, usually not more than 2 to 4 cm. tall; abundant on Bogue Beach after winds; large pieces 

 occasionally floating in the harbor, at times becoming fairly abundant; extremely abundant throughout 

 harbor and on Fort Macon and Shackleford jetties, April and May, attached and floating, often up to 

 i m. long; abundant in Newport River near Green Rock, August, 1906, forming large sheets resting on 

 the bottom; and extremely abundant North River off Lennoxville, July, 1906, floating in large masses 

 along shore. Pamlico Sound, Ocracoke, N. C. : Very abundant on shells, August, 1907. Core Sound, 

 on jetty at Davis Island: Abundant, about 2 to 3 cm. tall. Wrightsville Beach, N. C. : Fairly abundant 

 on shells in sound, July, 1909. Southport, N. C.: Very abundant, August, 1909. Georgetown, S. C.: 

 Fairly abundant, August, 1909. 



A very common plant throughout the world and extremely variable in form, thickness, and color. 

 Two fairly marked types can be distinguished in the species as found with us on both Atlantic and 

 Pacific coasts, connected by innumerable forms. 



Var. rigida (Agardh) Le Jolis. 



Ulva rigida, Agardh, 1820, p. 410 (in part). 

 Ulva lactuca, a rigida, Le Jolis, 1863, p. 38. 

 Ulva lactuca var. rigida, Farlow, 1882, p. 42. 

 Ulva lactuca forma rigida, De Toni, 1889, p. in. 

 Ulva lactuca var. rigida, Collins, 1909, p. 215. 

 P. B.-A. Nos. 407, 2064. 



Frond at first lanceolate or ovate; lanceolate, firm and stiff, with a distinct stipe; later somewhat 

 irregularly divided, and often with numerous perforations of various sizes; cells vertically elongate in 

 cross section. 



Var. latissima (Linnaeus) De-Candolle. 



Ulva latissima, Linnaeus, 1753, vol. 2, p. 1163. 



Ulva lactuca var. latissima, De-Candolle, in Lamarck and De-Candolle, 1805, tome 2, p. 9. % 



Ulva lactuca var. latissima, Farlow, 1882, p. 43. 



Ulva lactuca forma genuina, De Toni, 1889, p. in. 



Ulva lactuca var. latissima, Collins, 1909, p. 215. 



P. B.-A. Fasc. D, No. LXXVI. 



Frond irregular in outline, soon becoming detached and passing most of its life in a floating condi- 

 tion; thinner than var. rigida, lighter colored, and with cells nearer square in cross section. 



Both of these forms seem to occur at Beaufort , but are not sharply distinguishable . In the immediate 

 vicinity of Beaufort this species, like the species of Enteromorpha, reaches its greatest development 

 in the spring months. At other times of the year it is present mostly in the form of specimens 2 to 4 

 cm. long attached to rocks. Large masses are, however, found in summer in adjoining waters and 

 occasionally occur in Beaufort Harbor. 



