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On woodwork of old tidemill, forming a dense coating at high water mark, South Harpswell, Maine.

On tussocks in the tundra, St. Michael's, Alaska.

Floating, Sitka, Alaska.

Growing in dense tufts on stones in esturary, Cutler, Maine.

On sides of rock pools, lower litoral, exposed shore, Marblehead, Massachusetts.

On grass etc., in pool by Rooster River, Bridgeport, Connecticut.

Forming yellowish green floating masses in a small, brackish pool, Amaknak Island, Alaska.

Along the shore, Yakutat, Alaska.

On old plants of Cladophora, with Calothrix crustacea, in upper tide pool, rocky shore, Cohasset, Massachusetts.

Floating in slightly brackish water of Crocket's Lake, Whidbey Island, Washington.

Among Cylindrospermum stagnale, forming a scum on a small artificial pond, Pogy Oil Factory, Round Pond, Maine.

In high pool, Cape Rosier, Maine.

Washed ashore, Starboard Island, Machiasport, Maine.

Growing in dense masses below low water mark, Marblehead, Massachusetts.

On Nitella, Cold Spring Harbor, Long Island, New York.

In pools on exposed rocky shore, lower litoral, Pemaquid Point, Maine.

Attached to stones in running water, Lake Chabot, San Leandro, California.

Forming extensive loosely floating masses, in large shallow rock pools, Cape Rosier, Maine.

In quiet water, Minneapolis, Minnesota.

Lying loose on rocks, upper litoral, Departure Bay, Vancouver Island.

On grass stalks and mussels in shallow marsh pool, Bridgeport, Connecticut.

In pools at half tide, Easton's Point, Newport, Rhode Island.

On rocks, litoral region, ocean shore, St. John's, Newfoundland.

On stones one half to one meter below low water mark, mouth of harbor of Pictou, Nova Scotia.

Kingston, Jamaica.

On stones in brackish lake, near Summer Bay, Alaska.

Outlet of Ox Bow Lake, near Lake Piseco, Adirondack Mountains, Hamilton County, New York.

On stones in rapid water, Spot Pond Brook, Virginia Wood, Middlesex Fells, Massachusetts.

On rocks at low water mark, in company with F. edentatus, Appledore Island, Isles of Shoals, New Hampshire.

On rocky shore, nearly at high water mark, Easton's Point, Newport, Rhode Island.

on holdfast of Alaria fistulosa, at 10 to 20 meters depth, near Illiliuk, Alaska.

Among Spartina, etc., on mud flats near high water mark, Mattapoisett, Massachusetts.

Floating, South Harpswell, Maine.

Upper litoral zone, Marblehead Neck, Massachusetts.

On rocks, lower litoral, Eagle Island, Casco Bay, Maine.

Amaknak Island, Bay of Unalaska, Alaska.

In a brook, Bridgeport, Connecticut.

Orcas Island, Washington.

On stones at low water mark, Pacific Beach, San Diego County, California.

On rocks between tides, San Juan Island, Washington.

Floating in dense masses, Whidbey Island, Washington.

In shallow water, Lake Chabot, San Leandro, California.

On Galaxaura, etc., Santurce, Porto Rico.

East shore of Amaknak Island, Bay of Unalaska, Alaska.

San Juan Island, Washington.

In stellate tufts, rather sparsely distributed on various filamentous algae, in swamp, Medford, Massachusetts.

On Digenia simplex, etc., Santurce, Porto Rico.

Carmel Bay, California.

Montain Lake, San Francisco, California.

Cultivated in Botanical Laboratory, University of California, Berkeley, California.