250 NEMATOGENE. 
Mack. Hib. 239. Gray. Arr.i., 281. Eng. Fl. v., 374. Eng. 
Bot. ii., 2525. 
In ditches, swamps, inundated places, now and then free 
swimming; throughout the year. 
Very variable, passing into several moderately distinct varieties, of 
which the bright green one called viridis is the most beautiful, and by 
no means rare. 
The form which Carmichael called Oscillatoria contexrta has thus been 
described by him :—“ Stratum of indetinite extent three feet and up- 
wards, exceedingly thin, and peeling off in large flakes in dry weather, 
of adeep but shining black colour, scored or striated in all directions. 
These stri~# are caused by thick fasciculi of filaments, shooting out 
either parallel to or across each other, changing their course from time 
to time and sending off lateral fasciculi. The filaments are rather thick 
about a line in length, straight. or variously curved, of a greyish green 
colour, and they radiate with great rapidity. A portion of the stratum, 
not more than a line in diameter, placed in a watch-glass filled with 
water, overspread the whole area of the glass with filaments in the 
course of a night.” Hassall says of it, “ the filaments are in calibre not 
less than those of O. tenuis, from which species it is distinguished 
chiefly by its colour.” 
Plate XCVI. fig. 8. Portions of trichomes x 400. Plute XCVII, 
jig. 1. Portions of trichomes of the variety viridis X 400, 
Oscillaria antliaria. Jurgens Alg. Exs. No. 14. 
Expanded in a gelatinous, sometimes very broad submem- 
branaceous stratum, dark steel-blue. Trichomes rigid, straight, 
sometimes tranquil, sometimes oscillating, curved at the attenu- 
ated apex (curvature of 3 to 4 joints) ; joints equal, or nearly 
equal,in length and breadth (after division half as long), dissepi- 
ments distinctly granular, extreme apex obtusely rounded. Cell- 
contents pale steel-blue, or blue green, nearly homogenous. 
Size. Threads -0045-:0055 mm. diam. 
Kutz. Tab. Phyc. i, t. 40, f. 6. Rabh. Alg. Eur. ii., 100. 
Oscillaria parietina, Vauch. Conf., t. 15, f. 8. 
Around pumps, cisterns, &. 
Plate XCVII. fig. 2. Portions of trichomes x 400. 
Oscillayia muscorum. Carm, MSS. 
Stratum 8-4 inches, of a dark bluish-green colour, slightly 
lubricous, shortly radiating, creeping over mosses. Trichomes 
variously curved, pale blue green, joints about equal in length 
to their diameter. 
Size. Trichomes -006--007 mm. diam. 
Hook. Eng. Fl. v., 865. Harv. Man. 164. Hass. Alg. 
252, t. 72, f. 12. 
In rapid streams, on Hypnum ruscifolium, &e. 
** Stratum 3 or 4 inches in extent, closely interwoven with the branches 
and leaves of mosses, of a bluish green colour, and slightly lubricous 
