LYNGBY. 253 
Oscillaria chalybea. Mertens, in Jurgens Alga. 
Floating. Stratum broadly expanded, with long radii, dark 
blue green or steel-blue, shining; trichomes pale steel-blue, 
slightly flexuous, a little attenuated at the apex, joints three or 
four times shorter than their diameter, a little contracted at the 
dissepiments, which are not granulated, apiculus slightly curved, 
obtusely rounded, now and then rostellate, cell-contents pale 
steel-blue, granular, 
Size. Threads :0088--01 mm. diam. 
Kutz. Tab. Phyc. i, t. 40, £8, RKabh. Alg. Eur. ii, 108. 
In still and stagnant water. 
The specimens figured were collected from a tank in one of the stoves 
of the Royal Botanic Gardens, Regent’s Park. 
Plate XCVIII. fig.1. Trichomes of O. chalybea X 400 diam. 
Oscillaria Frolichii. Kutz. Phyc. Gen. 189. 
Stratum dark steel-blue, or at first olive, then dark blue, 
often elongated, radiating, opaque, shining; trichomes nearly 
equal, straight ; joints 2, 3, or 4 times shorter than their 
diameter, with a double series of granular points more or less 
dense at the junction, often confluent, so as to resemble a single 
series ; apiculus broadly rounded, straight, or declined; cell- 
contents blue, becoming steel-blue, homogenous. 
Size. Threads ‘015-018 mm. diam. 
Kutz. Tab. Phyc.i., t. 48, f.1. Rabh. Alg. Eur. ii., 109. 
Oscillatoria mucosa, Hass. Alg. 247, t. 71, f. 1. 
In ditches, pools, and boggy places, sometimes amongst 
mosses. 
The finest of the species yet detected in Britain. 
Plate XCVII. f.'7. Portions of trichomes x 400. 
Oscillaria insignis. Thwaites in Phyc. Britt, 
Stratum thin, covering decayed vegetable matter at the 
bottom of a ditch, with a dark-brown coating, becoming some- 
what greenish in drying; trichomes very large, rather brittle, 
their apices rounded, somewhat oblique, and furnished with 
numerous motionless cilia; cell-contents distinctly granulose. 
Size. Trichomes ‘018 mm. with sheath. 
Rabh. Alg. Eur. ii., 298. Harv. Phyc. Brit. ii, t. 251, f. ¢. 
In a brackish ditch. November. 
A portion of the trichome from the original specimen has been 
figured, but Professor Harvey was evidently of opinion that it was a 
strictly marine species, There seems at least to be no doubt that it is 
