English Soils : an Important Factor in Soil Biology . 7 1 
14. Nitzschia obtnsa , W. Sm., var. scalpelliformis , Griin. (Text-fig. 10 , 7). 
A small form of this diatom was found in one of the soils. The 
length of the valves was only about 45 jm, but they were abruptly sigmoid 
and showed at the middle of their length a distinct inflexion. At this point 
there was a rudimentary nodule lying between the two median carinal 
points, which were somewhat separated from one another. There were 7-5 
carinal points in 10 /x and 2 6 striations. 
15. Nitzschia Palea , (Kuetz.) W. Sm. (Text-fig. 10 , 8-10). 
This diatom occurred in the cultures of two soils. The valves were 
linear-lanceolate with capitate 
apices, and 11-12 carinal points 
in 10 jji, distributed regularly 
along the margin of the valve ; 
the striations were too faint to 
be made out. The length of 
the valves was about 29 to 33 /x, 
and the breadth about 4 ji. 
var. fonticola , Grun. (Text- 
% 10, u ). 
A diatom very closely re- 
sembling this variety was found 
in one soil. The valves had 
strongly capitate apices and 
there were 2 5 carinal points in 
10 fx, while their length was 
about 1 5 /x and breadth 3-5 yu ; 
the striations could not be made 
out clearly. The valves, how- 
ever, seemed to be slightly sig- 
moid, but this character, taken 
in conjunction with the others, 
does not seem sufficient to 
justify the separation of this 
form from the above variety. 
1 6. Nitzschia inconspicua , Grun. (Text-fig. 10 , 3-6). 
A number of very minute forms of Nitzschia, never exceeding 16 /x in 
length, were found in six of the soils, and though not in exact agreement 
with N. inconspicua , Grun., they should probably be regarded as forms of 
this species. 
The form most nearly in agreement with the description of this species 
(Text-fig. 10 , 3 and 4) was lanceolate with rounded ends and had 13 to 14 
carinal points in 10 /x ; the striations were too faint to be seen. The valves 
were 15 to 1 6 [i long and about 4 fx broad. 
Text-fig. 10 . Soil-diatoms III. land 2 flantzschia 
amphioxys, (Ehr.) Grun. ; 3-6, Nitzschia inconspicua , 
Grun. ; 7 , Nitzschia obtusa , (W. Sm.) var. scalpelliformis , 
Grun.; 8-10, Nitzschia Palea, (Kuetz.) W. Sm. ; 11, 
Nitzschia Palea, var. fonticola, Grun. All figs, x 1435. 
