1 70 Staple don. — On the Plant Communities of Farm Land . 
urged that, although Spergula arvensis and Chrysanthemum segetum are 
certain indications of ‘ sourness they are not confined to sands alone. It 
will be noted that less than 25 per cent, of these ‘sour’ soil plants are 
calcifuge species, suggesting that circumstances influencing the available 
water of the habitat, aeration, and other environmental factors exert as much 
influence as the absence of lime as such. 
It is of interest to observe that the Mid -Wales soils, although ranging 
from clay to stiff loam, do not include Ranuncidus arvensis in their weed 
communities, and that such plants as Stachys palustris , Euphorbia exigua , 
Galium Aparine, Potentilla reptans, Agropyron repens , and P apaver Argemone 
arc not at all generally distributed. Euphorbia Helioscopia , on the other 
hand, is probably as frequent on these soils as on those of a more calcareous 
nature. 
III. The Communities of Mid- Wales above and below 8oo'. 
Smith and Moss ( 9 ) and Moss (6) have pointed out that the limit of 
Wheat cultivation corresponds roughly with the limits of a number of weeds. 
Wheat is not grown on an extensive scale in the area now under considera- 
tion, but a number of farmers at altitudes below about 800' grow a small 
breadth for home consumption. Oats are grown up to about 1,400', and 
Barley is often to be seen considerably above 1,000'. Moss (6) has shown 
that the altitudinal limit of wheat cultivation is different on the various 
soils of the Peak district, but the average range is from about 500' to 900'. 
In this district the general method of husbandry is usually somewhat 
different above about 8oo' than below it, so that the 8oo' contour is 
a useful line of demarcation for purposes of comparison. The chief 
differences in the farming at high altitudes, apart from the absence of 
Wheat, are that the Brown Oat ( Arena strigosa) is more extensively 
grown ; Mangolds are only grown to a slight extent ; and the grass is 
left down for a longer period than is the case at lower elevations. 
Furthermore the arable farming is usually negligent ; the hoe is frequently 
inactive ; and the grass and clover seeds used are poor in quality, full of 
impurities, and inadequate. The effect of these primitive methods of 
husbandry on the weed flora will be shown to be considerable. 1 
Moss (6) has listed some forty odd species for the area studied in the 
Peak district as not occurring on both the Wheat and no-Wheat zone, 
practically all of these being absent from the higher elevations. 
A comparison of columns 3, 6, 9 (no-Wheat zone, i.e. above 800') with 
2, 5, 8 (Wheat zone, i. e. below 800') in Table I shows the following 
differences for Mid -Wales : 
1 It is perhaps most marked in the case of the grass-land. See Part II, 
