English Soils : an Important Factor iji Soil Biology. 77 
1 6. Stichococcus nitens , ( YAebs)=Hormidium nitens , Menegh. em. Klebs. 
In the cultures of one of the soils there appeared an alga which agreed 
in its characters very closely with Hormidium nitens , Menegh. em. Klebs, 
but the filaments were observed to be arranged more or less parallel to one 
another to form an expanded stratum, and were often completely disarticu- 
lated into single cells. Rarely short filaments were formed consisting of 
2 to 4 cells, and sometimes long normal filaments could be observed. This 
mode of growth is entirely that of a Stichococcus , and its occurrence in 
a form that has previously been regarded as a species of Hormidium rather 
helps to indicate that the latter genus is based on somewhat unstable 
characters. The extraordinary confusion existing among the species of 
Ulothrix , Hormidium , and Stichococcus makes it wellnigh impossible to dis- 
tinguish between Hormidium and Ulothrix on the one hand and between 
Hormidium and Stichococcus ori the other ; hence, pending further investiga- 
tion,, it seems best to regard the present form as a species of Stichococcus 
rather than of Hormidium. The cells were 5 to 6/x broad and 8 to 1 5 /x 
longij frequently about 9 ju. The single parietal chloroplast extended 
usually from end to end of the cell and about two-thirds of the way round, 
and contained a single pyrenoid, or two in those cells about to divide. 
Disarticulation of the filaments was effected by the splitting apart and 
rounding off of the transverse walls of adjacent cells. 
17. Gongrosira terricola , n. sp. (Plate II). 
This new species of Gongrosira , found in soil-samples from three 
widely separated localities, differs from all others previously described in its 
terrestrial habit and in the basal or more rarely intercalary position of its 
zoogonidangia. In the latter character it most closely resembles G. Codio - 
lifer a , Chod., in which the zoogonidangia are intercalary in the upstanding 
filaments ; but the absence of a limy incrustation establishes it as separate 
from this species independently of the position of the zoogonidangia. 
The stratum is expanded, and the creeping filaments are closely inter- 
woven to form a pseudo-parenchymatous disc of distended cells. The 
upstanding filaments are usually comparatively short and tapering with 
obtuse apices; they are irregularly branched, either in small tufts (PI. II, 
Figs. B and G) or with false dichotomy (Figs. D and F). The basal cells 
are swollen, 11 to 16 \x in diameter. Those of the upstanding filaments are 
subcylindrical or distended, and may be irregular on account of a tendency 
to branch; they are usually 10 to 18 ju, long and 6 to 14 /x broad, with 
a single band-shaped or irregular chloroplast containing usually one 
pyrenoid, rarely two, or sometimes none. The zoogonidangia are generally 
basal (Figs. A and H), but more rarely may be intercalary in the upstand- 
ing filaments. They are usually subspherical or irregular, 14 to 18 /x in 
diameter or occasionally less, opening by means of a lateral pore to set free 
a large number of biciliate zoogonidia. 
