i 3 8 
W. B. Crump. 
association is very uniform over wide areas the humus-content 
varies considerably with the depth. The peat is as a rule so 
shallow that the heather roots regularly pass through it into the 
underlying coarse sandy soil that may be conveniently called the 
“ sub-peat.” The actual water-content of these two layers is not 
comparable, but physiologically the two seem indistinguishable, so 
that any satisfactory index of the humidity should have the same 
value for the two layers and thus be independent either of depth or 
humus-content. 
This heather moor, as developed on the Pennines is a well- 
known association. The analyses available represent a number of 
localities in west Yorkshire, and cover the average seasonal range. 
To make the association more definite, the wetter type of heather 
moor characterised by the presence of Erica Tetralix is excluded 
from the present enquiry. 
The results of the analyses are set out in the following table in 
order of the humus-content. As elsewhere in the paper the figures 
i., ii., iii. added to the soil numbers indicate corresponding layers of 
a section. There is no difficulty in distinguishing a peat from a 
sub-peat for the table shows that there is a sharp break between 
the two. It includes only one sample with a humus-content 
between 10% and 25%, so that whilst a sub-peat contains less than 
10 or 15%, a peat never contains less than 25% and rarely less than 
30% of humus. 
Heather Moor (Callunetum vulgaris). 
Peats : at 1 to 3 inches from the surface. 
No. 
Date. 
Moor. 
Water 
Loss 
at 15° 
% 
% of Air-dry Peat. 
Water. 
Loss at 
100° 
Humus. 
Mineral 
Residue. 
Humus. 
y 
X 
m 
207 i. 
April, 1912 
Greetland 
1682 
12-2 
70-8 
16-9 
2-4 
206 i. 
135-8 
10-7 
62-9 
26-4 
216 
37 
Mar., 1906 
Cold Edge 
139-4 
7-2 
49-6 
43-2 
2-8 
99 i. 
Aug., 1910 
Norland ... 
101-4 
8-7 
48-6 
42-6 
2-1 
63 
Aug., 1906 
Rumbles... 
99-1 
7-3 
400 
52-7 
2-5 
205 i. 
April, 1912 
Greetland 
83-9 
7-2 
38-4 
54-4 
2-2 
58 i. 
June, 1906 
Bellhouse 
90-8 
5-7 
37-6 
56-7 
2-4 
106 ii. 
Aug., 1910 
Erringden 
82-0 
6-5 
370 
56-5 
2-2 
11 
Sept., 1905 
Greetland 
730 
5*6 
36 - 5 
57-9 
2-0 
58 ii. 
June, 1906 
Bellhouse 
71-3 
50 
33-4 
61-6 
21 
106 i. 
Aug., 1910 
Erringden 
78-4 
6-4 
32-2 
61-4 
2-4 
38 
Mar., 1906 
Cold Edge 
84-7 
4-8 
30-7 
64-6 
2-76 
57 
June, 1906 
Bellhouse 
79-3 
5-1 
300 
64-9 
2-6 
145 i. 
June, 1911 
» » 
45-9 
4-7 
26-8 
68-4 
1-7 
Mean 
95-2 
6-9 
410 
520 
2-31 
