76 Bristol . — On the Alga- Flora of some Desiccated 
13. Ulothrix subtilis, Kuetz. 
The normal form of this species appeared in the cultures of five soils. 
The cells were 4 to 5 /x broad and about the same length. After sometime 
in the cultures the filaments were observed to break up into fragments con- 
sisting of a dozen or more cells, a character common to practically all of the 
filamentous forms growing in the cultures, 
var. variabilis , (Kuetz.) Kirchn. 
This variety of the species occurred much more frequently than the 
normal form, having been observed in twenty-seven soils. The cells were 
usually 8 to 9 /x broad and varied in length from 6 /jl to about 17 \x. There 
was a single parietal chloroplast extending practically the whole length of 
the cell and about two-thirds of the way round, and containing as a rule 
a single large pyrenoid in which the separate starch-plates could frequently 
be seen. In the winter months, however, the pyrenoid sometimes was not 
visible. After some time the filaments were observed to break up into 
fragments containing a comparatively 
small number of cells ; this was effected 
by the rounding off of the end walls of 
two adjacent cells. 
14. Ulothrix tenuissima , Kuetz. 
(Text-fig. 12 ). 
In one of the soils a species of 
Ulothrix was observed which differed 
from U. tenuissima only in the number 
of its pyrenoids. The cells were 18/x 
broad and 10 to 17/x long, with a firm 
thin wall. The chloroplast extended 
practically the whole length of the cell 
and about three-quarters of the way 
round the wall, and contained a single 
large pyrenoid in which it was some- 
times possible to detect the separate 
starch plates. In a single cell only, viz. 
in the end cell of the filament figured, 
there were two pyrenoids as has been 
described by Heering for this species. 
15. Stichococcus bacillar is , Naeg. 
The cultural conditions were such that the filamentous form of this 
species was very rarely observed, and such filaments as did occur consisted 
of not more than three cells. 
The alga thus entered into a unicellular condition, the cells being 
rectangular with slightly rounded ends, about 6 to 8 /x long and 2 to 2*5 M 
broad, with a parietal chloroplast devoid of a pyrenoid extending over about 
half of the surface of the cell. The species was found in four soils. 
Text- fig. 12. Ulothrix tenuissima , 
Kuetz.; fly., pyrenoid. x 825. 
