IO Rhodora [JANUARY 
3. U. FasciaTA Delile, Egypt, 153, Pl. LVIII, fig. 5, 1813; J. G. 
Agardh, Till Alg. Syst., part 3, 173, 1882; De Toni, Syll. Alg. Vol. 
I, 114, 1889. Frond divided into linear segments, margin smooth 
or undulate; in cross section the two layers of cells separate some- 
what at the margin, which is rounded, with a small open space 
between the rows. 
The structure of the frond in this species is similar to that of U. 
Lactuca, except the margin, which resembles Ænteromorpha Linza; 
but the shape of the frond with definite linear divisions is quite dis- 
tinct. These divisions may be dichotomous or apparently lateral; 
their width may vary from 5 mm. to 5 cm.; and the frond may reach a 
length of a meter; the margin may be quite smooth and even, or 
much crisped and undulate ; in this it corresponds to forms of Ænzer- 
omorpha Linza. Found on the east coast at Florida, and on the west 
coast along the whole of California: in warm waters all over the 
world. Harvey (1) 58; (2) 176. Farlow (2) 379; (3) 713. Her- 
vey (1) 54. Anderson (1) 218. Exsicc. Phyc. Bor.-Am., 221. 
. Three forms of this species have been distinguished on the Paci- 
fic coast, passing into each other more or less. 
Forma TAENIATA Setchell, Phyc. Bor.-Am., 862. Lobes slender 
and elongated, crisped and ruffled; prominent teeth on the margins 
near the base of the frond. 
Forma LOBATA Setchell, Phyc. Bor.-Am., 863. Lobes shorter and 
broader, seldom crisped or ruffled. 
Forma caesPrrosa Setchell, Phyc. Bor-Am., 809. Divisions 
numerous, irregular; fronds intricately entangled, forming a dense 
coating on the rocks. 
MONOSTROMA Thuret. 
Frond at first a. closed tube or sac, which later opens or splits, 
forming a membranous expansion, of a single layer of cells, except at 
the base, where it is thickened, and may consist of several layers of 
elongated cells. Zoospores formed in any of the cells of the mon- 
ostromatic part, issuing through an opening at the surface of the 
frond. 
In some of the species of this genus the saccate form has not been 
observed, but it probably occurs in all. Its persistence varies much, 
from M. /atissimum, in which the frond forms a flat expansion when 
only two or three mm. high, to M. Groenlandicum, in which the 
greater part of the frond continues tubular through its whole life, 
only the upper part opening at the time of the formation of the zoo- 
spores. Some of the smaller species do not exceed 1 dm. in length ; 
others, like M. Blyttii, may reach 5 dm. It has representatives in 
all oceans, and several species inhabit by preference brackish water ; 
