1920] Seichell-Gardner : Phycological Contrihutians 285 



margins they are nearly square. A younger specimen of this plant 

 was distributed by one of us as Ulva fasciata f. expansa (Phyc. Bor.- 

 Amer., no. LXXVII), but it has seemed, on further study, to belong 

 neither to Ulva fasciata Delile nor to the Ulva fasciata f. taeniata also 

 distributed by one of us (Phyc. Bor.-Amer., no. 809), but described 

 later on in this account as Ulva taeniata. We, therefore, describe it 

 as an independent species under the name of Ulva expansa. 



Ulva expansa, so far as we have observed it, remains attached only 

 for a short time. It soon becomes free and floats or drifts, increasing 

 in size, becoming at times at least 3 M. long and varying in width 

 from 18 cm. to 75 cm. In form and structure it differs from Ulva 

 latissima and from all the other species of Ulva of our coasts. It 

 comes nearest to Ulva fencstrata, as we have described that species, 

 but is little, if at all, perforate. Plants of what appears to be the 

 same species have been found in the Puget Sound region and Howe 

 (1911, p. 490) is inclined to credit here some from La Paz, Mexico. 



Ulva dactylifera sp. nov. 



Plate 26, figure 1 



Thallo sessili aut stipite brevi suffulto; parte basali obovata aut 

 reniformi, crispatissimo, 2-4 cm. alto, e margine superiore 1-6 lobos 

 aut lacinias, simplices aut sparse ramosos et costam definitam osten- 

 dentes et marginibus crispatissimis instructos producente, 5-15 cm. 

 high, 0.5-1.5 cm. wide; membrana basali ad marginem 50/x, ad medium 

 usque ad 100/x crassa, cellulis e superficie 16-20/x diam. sectione trans- 

 versali quadratis usque ad 2-plo diam, longioribus; membrana laci- 

 niarum marginibus 40-50/* crassa, medio usque ad 190/a crassa, cellulis 

 e superficie 12-16/t diam., sectione transversali quadratis usque ad 

 5-plo diam. longiores; chromatophoris dimidium externum cellularum 

 implentibus. 



Frond sessile or with a very short stipe ; basal portion orbicular 

 or reniform, much crisped. 2-4 cm. high, giving rise from the upper 

 margin to 1-6 lanceolate, simple or occasionally branched lobes or 

 laeiniae with plane midrib, and much crisped margins, 5-15 cm. high, 

 0.5-1.5 em. wide ; membrane of basal portion 50/a thick at the margin, 

 up to 100/x thick in the middle, with cells 16-20/i. diam. in the surface 

 view, quadrate to 2 times as long as wide in section, membrane of the 

 laeiniae 40-50/t thick on margin, up to 190/i thick in the middle, with 

 cells 12-16/1 diam. in surface view, quadrate to 5 times as long as wide 

 in section ; chromatophore filling the outer half of the cell. 



On exposed rocks, uppermost littoral belt. Southern California 

 to Mexico (San Roque?). Type no. 3988, Gardner. 



"We have along the Californian coast two species related to Ulva 

 fasciata, neither of which seems to be exactly like the Mediterranean 



