LYNGBYA.

221

of the cell, hut leaving a pellucid margin all around, sub-sequently becoming globular and granular. Zoospores sixor eight in each cell.

Conf. zonata Web et Morh. Corf, lucens Dillw. t. 47.Conf. bicolor, E. B. t. 2288. Spliceroplea crispa Berk.Glean. Algse, t. 3. fig. 1.

This species delights in pure and running water, it growingluxuriantly in that of cascades and waterfalls. It is every-where common throughout Great Britain . Considerable con-fusion seems to have prevailed relative to this plant, severalobservers having repeatedly described it under different names.I have no doubt whatever of the correctness of the synonymesquoted. The form of the cells in this species is somewhat pecu-liar. They are not exactly cylindrical, but taper graduallyfrom each extremity towards the centre of the cell, the ex-tremities, or angles of the cells appearing in consequenceprominent.

Two varieties of it have presented themselves to me; theone at Snaresbrook, Essex, in great quantity; this agree-ing with the species proper in all, save the length of thecells, which arc generally two and a half or three times aslong as broad; the other in a stream at Wood Green, nearCheshunt , in which the cells are cylindrical, completely filledwith endochrome, and not one third so long as broad. Thismay be distinct.

2. Lyngbya muralis Ag.

Plate LIX. Fig. 7.

Char. Filaments of less diameter than those of Lyngbyazonata, dark green, entangled. Cells very short, two orthree times broader than long.

Hab. On the ground in all damp situations early in thespring.

This is a very distinct species, rendered interesting fromthe peculiarity of its habitat. The diameter of the filaments