ULVA 19 
thick, becoming 200-750 и towards the stiff crisp rhizoid-filled 
basal parts. The cells in a cross section are 1-3 times higher than 
broad. In most of Dr. Coker’s specimens the two layers separate 
very easily. We at first suspected that this tendency to separate 
might be due to four or five years’ keeping in a formaldehyde 
solution, but it has been discovered only in the specimens that we 
have identified with the rigida form while in specimens that we 
have referred to the latissima form and to U. fasciata, preserved 
іп the same way, there is no trace of this peculiarity. Іп one case 
(193—U. Lactuca rigida and U. fasciata costata) the forms with the 
easily separable and firmly coherent layers occur under a single 
collection number, in which case the general mode of handling as 
well as the character of the preserving medium may fairly be 
presumed to have been essentially identical for both. 
Ulva Lactuca rigida was collected at Callao (in 1839) by the 
Wilkes Expedition according to a specimen in the Columbia 
College Herbarium, under the name Ulva latissima. 
“Опа umbilicalis” was attributed to Рана, Peru, by Bory 
(Voy. Coquille, Bot. Crypt. 188, 189. 1828); Ulva Lactuca has 
been reported from Callao by Montagne (FI. Boliv. 5. 1839); 
Piccone (Alg. Vettor Pisani 21, 23. 1886) has recorded Ulva 
myriotrema Crouan from the Callao region and Ulva fasciata lobata 
(Kütz.) from Рана; we have not-seen any of these specimens but 
suspect that we should place them all with Ulva Lactuca rigida. 
ULvA LACTUCA LATISSIMA (L.) DC. Fl. Fr. 2: 9. 1805 
Ulva latissima L. Sp. Pl. 1163. 1753. J. Ag. Till Alg. Syst. 3: 164. 
1882. 
Dredged in Ancón Bay in 9 fathoms, on a mud bottom, Feb. 
13, 1907, Coker до р.р.; in the surf, Lobos de Tierra, Apr. 2, 1907, 
Coker 151 p.p.; in lagoon at La Puntilla, Bay of Paracas, region of 
Pisco, June 29, 1907, Coker 00610 p.p. 
The specimens grouped together under this varietal or form 
name are diversified in form, size, and color, but agree in having a 
thin thallus (13-40 и thick) and in having cells that are broader 
than high or subquadrate in section. One of the two Ulva frag- 
ments collected under no. 09619 is exceedingly thin (13-15 и) 
and adheres very firmly to paper, suggesting in both respects 
certain species of Monostroma, but it is distromatic. 
