244 THE JOURNAL OF BOTANY 
crass. ram. 1-7-8 p (figs. 11-16). Hyeravellir, temp. 55° C.; also 
in the spray of a small geyser (temp. of spra 85° C.). In stream 
from the Great Geyser, mean temp. about 40° C. In all cases the 
specimens were partly encrusted with carbonate of lime. 
he primary filaments of this plant possessed a well-marked 
sheath, sometimes thin with parallel edges, sometimes @ little 
thicker with undulate margins, and ale yellow in colour. e 
cells were globose, ellipsoidal, or oblong with rounded en The 
branches are usually horter and thinner than the primary 
. - 
and cylindrical, from 1 -6 times longer than their diameter. 
Heterocysts subglobose in the primary filaments, and cylindrical 
11. Nostoc muscorum Ag. Crass. trich. 8-3'5 p; cells 14-1% 
times longer than their diameter. In expanded gelatinous sheets, 
Hveravellir, temp. C. 
12. Nostoc pruniforme Ag. A variety with a thin, contorted, 
lacerated thallus; cells subglobose or a little longer than their 
diameter, with their adjacent poles slightly flattened. Crass. trich. 
5-7-6°5 p. Hyveravellir, temp. 49 C. 
13. Aulosira thermalis, sp. n. (figs. 1-10). Filis eruginels, 
: si a rtis 
catissima et hyalina; trichomatibus facile dissociatis, 
li 
ellulis vegetativis subglobosis, ellipsoideis vel suboblongis; hetero- 
cystis sparsis, subquadratis vel oblongis, cellulis vegetativis vis 
Qa < 
= 
2 
catenatis. Crass. trich. 2°8-3°2 ; crass. heterocyst. 8°5-8'8 p; ons 
heteroeyst. 5°7-8'8 p»; crass. spor. 3°8-7°7 p»; long. spor. 8-8-18'5 pi» 
Hyeravellir, in great abundance at temperatures from 55°-61" ©. 
8 
ells of the ordinary vegetative trichomes are mall, sub- 
spherical, or a little longer than their diameter. The cell-contents 
appear to be absolutely homogeneous, of a pale blue- 
in diameter. The ripe spores exhibit numerous granules 10 th 
cell-contents. Se 
O"thermalis is about half the size of any of the other species 
the genus, and, in addition, it can easily be recognized by the ole 
aggregation of the filaments. 
14. Phormidium luridum (Kitz.) Gomont. Crass. trich. 1:9-2 
long. cell. 1-9-8 ». Hveravellir, temp. 88° C. 
