Phycotheca Boreali-Americana Collins, Holden & Setchell.

1714. Plectonema roseolum Gomont.

Gomont, Monogr. des Oscill., p. 122, Pl. I, fgs. 9 & 10, 1893.

Forti, Syll. Myx., p. 494, 1907.

Tilden, Minn. Algae, Vol. I, p. 210, Pl. XI, fig. 8, 1910.

On window of conservatory, University of California, Berkeley, California, May 16, 1906.

N. L. GARDNER.

1715. Tolypothrix tenuis Kuetz.

Kuetzing in Bornet & Flahault, Revision des Nost. Het., part 3, p. 122, 1887.

Forti, Syll. Myx., p. 545, 1907.

Tilden, Minn. Algae, Vol. I, p. 229, 1910.

In company with T. lanata Wartmann, forming a coating on a wooden chute, Icehouse Pond, Eastham, Massachusetts, Sept., 1909.

F. S. COLLINS.

The extremes of size in this material are quite typical of the two species mentioned, but there are intermediate forms that cast some doubts on the distinctness of the two species.