round water-pipes or wells. Stratum thin, bright green. Trichomes radiating and actively oscillating, 4-8/* thick, generally a little constricted at the joints. Two varieties occur in Lahore, one with straight broad apex, and the other with curved and a little attenu- ated apex.
Osciliatoria terebriformis Gom. (De Toni, I. c. p. 189) is generally found forming a green scum on stagnant ponds, associated with Clathrocystis csruginosa and Arthrospira Tenneri Kuetz. Trichomes free swimming, flexible, screw-shaped or in lax spiral, with unconstricted and indistinct joints, 4-6/x thick ; apex generally drawn out.
The Sub-family Spirulinecs is represented by Arthrospira Jenneri Kuetz. (De Toni, I. c. p. 206; Cooke, p. 245, pi. 96, fig. l) which, as mentioned above, is generally found associated with Clathrocystis csruginosa and Osciliatoria terebriformis. Trichomes bright green, elongated, 4-6/* thick. Spirals 10-16/* in diameter, and about 8/* distant. Joints distinctly constricted ; cells globose.
Of the Sub-family Lyngbyecs, Phormidium is more frequent than Lyngbya. Phormidium ladinianum Gom. (De Toni, l.c. p. 218) has been found on tree trunks, especially on that of Acacia modesta, associated with Phormidium Hansgirgi Schm. and Tolypothrix byssoidea Kirchn i Stratum dark green, thin, fibrous. Trichomes straight, flexible, constricted at the joints, 4-6/* thick. Sheath thin, hyaline. Contents granulose, sometimes hyaline in the centre. See Fig. 3.
Phormidium tenue Gom. (De Toni, I. c. p. 227) generally sticks to the submerged walls of artificial tanks, forming a membranous, expanded, dirty green stratum on the mud. Trichomes long, a little curved and densely intricate, slightly constricted at the joints, 1-2/* thick.
Phormidium Hansgirgi Schm. (De Toni, I. c. p. 235) is found on tree trunks, associated with Tolypothrix byssoidea and Phormidium ladinianum, forming a dark bluish-green stratum. Trichomes parallel, 10-12/* thick, with broad convex apex. Sheath hyaline when moist, and dirty brown and fragile when dry. See Fig. 4.
Phormidium Moerlianum Grun. (De Toni, I. c. p. 236) is found in stagnant water, where decaying vegetable matter is present. It is generally associated with a species of Oedogonium. Trichomes long, a little curved, brownish, 9-12/* thick ; joints very short. Sheath thin, colourless. Dissepiments granulated. See Fig. 5.
Lyngbya aestuarii Lieb. (De Toni, I. c. p. 262 ; Cooke, I. c. p. 258 pi. 101 fig. l) is commonly met with, associated with a species of Oedogonium, and forming freely floating greenish masses. Trichomes long, flexuous, blue-green, granular, about 40/* thick; joints very short. Sheath hyaline, clearly lamellose and brownish when old.
