1903 | Collins, — The Ulvaceae of North America 9 
63. Bennett (1) 95. Martindale (1) 92. Collins (7) 246; (8) 45. 
U. rigida Harvey (2) 176. Murray (1) 260. Britton (1) 400. 
Saunders (1) 410.  Exsicc. Amer. Algae, 124, 260; Pnyc. Bor. 
Am., 407. 
Var. LATISSIMA (L.) DC., Fl. Fr., Vol. I, 9, 1805. Frond irregu- 
lar in outline, soon becoming detached and passing most of its life 
in a floating condition; thinner than var. rzgzda, lighter colored, and 
with cells nearer square in cross section. 
This is a common form of creeks and lagoons, where it forms 
floating sheets, often of several square meters in extent. Itis doubt- 
ful if this variety corresponds with the U. /atzssima of Agardh; more 
probably both the varieties here given are included in the various 
forms given by him under .U. rigida; his U. Zatissima is given as 
occurring only in the German Ocean and the Baltic, and, with some 
doubt, on the French coast and in the Mediterranean. It is not easy 
to find from his description just what the difference is between his 
U. latissima and his U. rigida “formae b, substantia tenuiores 
exsiccatione membranaceae.” Collins (6) 77. Bennett (1) 9s. 
Britton (1) 400. Martindale (1) 92. 
Var. MESENTERIFORMIS (Roth) Collins (8) 45; U. mesenteriformis 
J. G. Agardh, Till Alg. Syst. part 3, 163, 1882; De Toni, Syll. Alg., 
Vol. I, 103, 1889. Frond much contorted and bullate, forming 
crumpled masses, lying loose on the bottom. 
This form is strikingly distinct in appearance, forming much 
crisped and wrinkled masses, usually of a dark green color, lying on 
the bottom in creeks and quiet bays. It is so twisted and grown 
together that only by tearing can even a small piece of it be spread 
out flat. In cross section the cells are nearer square than those of 
the type. Itis common in marshy ponds near Bridgeport, Conn., and 
will probably be found in similar places. Known elsewhere only in 
the Baltic. 
2. U. CariFoRNICA Wille. Frond 1.5 to 2 cm. long, up to 1.5 
cm. wide, triangular or reniform with wavy edge, sometimes with 
proliferations of a few cells each; passing quickly into a flattened 
tapering stipe. The cells of the stipe, which on the inner side of 
each layer form rhizoidal prolongations, are in cross section about 
quadrate, or a little longer tangentially. The cells in the upper part 
of the frond are, seen superficially, nearly isodiametric, somewhat 
irregular in form, with rounded corners; longer and shorter cells 
alternate, but the longitudinal series are quite inconspicuous. The 
upper part of the frond is about .o3 mm. in thickness. 
A species with minute fronds, with more definite outline than is 
usual in species of this genus. It is known only from Pacific Beach, 
San Diego County, California, where it is reported by Mrs. E. Sny- 
der as forming a rather dense coating on rocks near high water mark. 
Exsicc. Phyc. Bor.-Am., 6rr. 
