42 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



ULVA Linnaeus, 1753 



Plants becoming expanded, foliaceous, attached or becoming free 

 floating; simple and orbicular to elongate and laciniate, plane or crisped; 

 of two cell layers, the cells showing single chromatophores with pyrenoids. 



KEY TO SPECIES 



1. Cells of the central portion little taller than broad, rectangular 

 in section U. Lactuca 



1. Cells of the central portion of the blade much taller than broad 

 2 



2. Mature thallus deeply lobed with plane or ruffled margins ; mem- 

 brane 45-90 fi thick, the cells 2.5 times as high as broad . . . 

 U. lobata 



2. Juvenile thallus deeply lobed with plane or ruffled margins, 

 mature thallus deeply divided into long, narrow, crisped seg- 

 ments; thallus in the juvenile state to 100 ju, thick in the center, 

 the cells to twice as tall as broad, in the adult state to 190 /* thick, 

 the cells to 5.0 times as tall as broad U. dactylifera 



Ulva Lactuca L. 



Collins 1909, p. 214; Taylor 1937, p. 75, pi. 4, fig. 6; Smith 1944, p. 

 45, pi. 3, figs. 6, 7. 



In one form or another a common plant of cosmopolitan distribution 

 in the littoral and sublittoral belts, growing on solid objects, but in quiet 

 water often continuing to develop if disengaged. 



Mexico: Is. Revilla Gigedo, frequent as dredged at sta. 135 from 45 

 meters' depth off Sulphur Bay, I. Clarion, no. 34-48A, 5 Jan. 1934. Ibid., 

 rare as dredged at sta, 136 from 57 meters, no. 34-67, 5 Jan. 1934. Ibid., 

 juvenile plants on shore rocks, no. 39-16, 16 Mar. 1939. Ibid., dredged 

 from 51-79 meters' depth at sta. 917, no. 39-22, 16 Mar. 1939. Costa 

 Rica : abundant on rocks at mid- and low-tide levels. Port Parker near 

 Ba. Salinas, no. 39-75, 25 Mar. 1939. Ecuador: Archipielago de 

 Colon, small plants on intertidal rocks, I. San Salvador, no. 34-348, 24 

 Jan. 1934, Ibid., abundant but juvenile from Rhizophorn roots over 

 white mud in a lagoon near buildings, Academy Bay, I. Santa Cruz, no. 

 34-301 J, 20 Jan. 1934, Ibid., dredged from a sandy bottom at 36-55 

 meters near an islet in Gardner Bay, I. Espaiiola, no. 34-409, 31 Jan. 

 1934. Guayas, littoral rocks near Salinas, Schmitt no. 503, 12 Sept. 

 1926. 



