Stcipledon . — On the Plant Communities of Farm Land. 165 
For some species the range of frequency is given (thus e.g. 4-8) ; in 
most cases the average frequency only is given (e.g. s, 5, or 8) ; in some 
cases as well as the average frequency an exceptionally high frequency is 
given (e.g. 3 the normal and (8) the exceptional figure). 
I. Comparison of the Flora of the Cotswolds with that of Mid- Wales. 
The soils of the two districts are very different ; that of the Cotswolds 
is derived from the Great Oolite and is a highly calcareous loam. 
The soils investigated in Mid- Wales are derived from Ordovician Shales 
and give rise to a thin, very stony soil, which in wet weather is very sticky 
(due to a high percentage of fine silt) and in dry weather tends to cake 
badly and form pan ; under favourable conditions, however, it works into 
a friable loam. 
Below (Table II) is given a typical chemical and mechanical analysis 
of each soil. For the Mid-Wales figures I am indebted to my colleague 
Mr. Jones Griffiths; the Cotswold results are quoted from Kershaw’s ( 5 ) 
analyses. 
Table II. 
SYNOPSIS OF MECHANICAL AND CHEMICAL ANALYSES OF 
COTSWOLDS AND MID-WALES SOILS. 
Mechanical Analyses. 
Mid- Wales. 
Cotswolds. 
Fine Gravel 
20-3 
i *5 
Coarse Sand 
13*5 
i*6 
Fine Sand 
8-4 
Coarse Silt 
12*6 
13*4 
Fine Silt 
20*8 
15*3 
Clay 
7-8 
13-8 
Chemical Composition. 
Mid- Wales. 
Cotswolds. 
Nitrogen 
o -39 
0-38 
Lime (CaO) 
0-15 
11*27 
Phosphoric Acid (P 2 0 5 ) 
o-ooS 
0*24 
Potash (K s O) 
o*86 
0*41 
Available Phosphoric Acid 
0-002 
0-007 
Available Potash 
0*04 
0*011 
The above figures show the Mid- Wales soil to be very deficient in lime 
and phosphoric acid, the Cotswold soil to be very rich in lime and 
relatively rich in phosphoric acid. Considering the marked difference in 
the two soils the number of species which occur in the one district and 
not in the other are comparatively few. The following are, however, 
characteristic : 
