20 ULVACEAE 
Ulva fasciata costata forma nova 
Ulva fasciata Bory, Voy. Coquille, Bot. Crypt. 190. 1828. Vix 
Delile. 
Thallus or its main divisions narrow and elongate (usually 
20-70 cm. X 0.5-2 cm.), crisped and ruffled and often spirally 
contorted, sometimes pinnatifid near base, more or less distinctly 
costate, the costa mostly 120-150 и thick, twice as thick as Ше 
remaining lamina, the margins sinuate or obscurely dentate, the 
marginal cells commonly protuberant (i. e., margins commonly 
concave or emarginate in a cross section); zoosporangia (?) or 
gametangia (?) in darker-green marginal bands. [PLATE г; 
LATE 2, FIGURES 10-23.| 
Chincha Islands, on surf-washed rocks, June 18, 1907, Coker 
193 p.p. | 
The costa is of a lighter color than the remaining thallus and is 
composed of more vacuolate and vertically more elongate cells, 
reinforced toward the base by numerous rhizoidal medullary 
hyphae. In our fluid-preserved material the costa, which vanishes 
near the apex, is often so conspicuous and sharply defined as almost 
to suggest an Alaria, but in other cases it is indistinct and then 
the resemblance of the plants to the Californian U. fasciata f. 
taeniata Setchell, as exhibited in Phycotheca Boreali-Americana 
862, is marked, though they are less dentate-margined than that. 
However, very similar plants evidently occur on the Californian 
` coast, as is shown by our copy of P. B.-A. 2210, issued as Ulva 
fasciata, which is apparently to be identified with forma costata. 
The fertile cells in the Peruvian specimen seem to be confined to 
a clearly marked longitudinal band or zone 1-3 mm. wide along 
each margin; at least, there is nothing in our material to indicate 
that this fertile area ever includes the costa or, in fact, really 
approaches it. In this apparent limitation of the fertile cells 
and in the possession of a costa and a thinner foliar lamina the 
plant seems to offer in some measure a transition to the genus 
Letterstedtia. 
It is to be noted that a cross section of the thallus does not 
show the semicircular arrangement of numerous marginal cells 
about a minute empty space that J. Agardh conceived to be pe- 
culiar to Ulva fasciata. The thallus may be composed of two 
parallel strata to the very margin (Fic. 20); or the marginal cells 
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