54 MARINE ALG 
in C. melagonium, which it otherwise resembles; tufts three to twelve 
inches long; cell-divisions very marked. This species is found in rock 
pools from Cape Cod to New York Bay. : 
C. linum. Bright green; filaments coarse, rigid, twisted together, 
and prostrate. It is found floating in masses and forming strata on 
rocks and gravel from New York northward. It is thought by some 
that this, as well as C. picquotiana, which it closely resembles, is not 
a true species, but consists of the mature plants of the species C. mela- 
gonium and C. erea, which have become detached from their holdfasts 
and have continued to grow. (Plate III.) 
GEenus Cladophora 
(''‘Branch-bearing "') 
Frond filiform, branched. There are many species of Cla- 
dophora, which differ from one another in their branching, color, 
and size. They abound on rocks at low-water mark, in tide- 
pools, in muddy ditches, and on wharves. They are especially 
characterized by being so profusely branched as to form tufts or 
spherical masses, by which the collector can easily distinguish the 
genus. 
C. arcta. Bright, glossy green; filaments fine, erect, much branched, 
two to eight inches long; tufts dense, more or less entangled, and in 
bunches, giving a starry effect. The species is common on rocks near 
low-water mark from New York northward. The plants vary slightly 
in appearance with the season. (Plate III.) 
C. rupestris. Dark green ; filaments straight, rigid, tufted ; branches 
crowded; many branchlets flattened against the filaments, so that the 
alga somewhat resembles grass; five to ten inches long. The cell- 
divisions show plainly. Plants of this species do not adhere to paper 
in drying. They are found on rocks at low-water mark, and are com- 
mon on the northern New England coast. (Plate III.) 
C. gracilis. Bright yellow-green; filaments very fine, loosely tufted, 
three to twelve inches long, soft, silky, much branched; branches rather 
short, and branchlets more or less curved _and arranged in a comb-like 
manner. It grows on wharves, in muddy pools, and on eel-grass. 
(Plate IV.) 
ORDER ULVACEZ 
The plants of this order are, with few exceptions, formed of 
celled surfaces and show the earliest type of an expanded leaf. 
The cells form thin membranes, which sometimes are broad sur- 
faces of no definite shape, sometimes are narrow and ribbon-like, 
or they may be simple or branched tubes. When the membrane 
