Stapledon. — On the Plant Communities of Farm Land. 169 
Table III. 
TO COMPARE THE WEED COMMUNITIES FOUND ON FOUR GRADES 
OF 1 SOUR ’ SOIL. 
r. 
2. 
A T on- 
3 - 
Non - 
4 - 
Chief Species. 
Peat. 
Calcareous 
Clay. 
Calcareous 
sticky loam. 
Sand. 
Ranunculus repens 
a-d 
a 
f-a 
o-f 
Papaver R hoe as 
— 
— 
— 
a-d 
Erophila verna 
— 
— 
r 
o-f 
Spergula arvensis 
a-d 
f-a 
a-d 
a-d 
Geranium nolle 
— 
r 
r-f 
f-a 
G. dissectum 
r 
o-f 
r-f 
r 
Potentilla Anserina 
r 
o-f 
f-a 
o-f 
Scabiosa succisa * 
a-d 
f-a 
r 
r 
Gnaphalitim uliginosum 
r 
f 
o-f 
f-a 
Achillea Ptarmica * 
o-f 
f 
r 
— 
Chrysanthemum segetum 
o-f 
r 
a-d 
d 
Centaurea nigra * 
o-f 
f-a 
o-f 
r 
Lycopsis arvensis 
— 
— 
— 
0 
Echium vulgar e 
— 
— 
— 
0 
Veronica hederaefolia 
— 
— 
r 
o-f 
Mentha arvensis 
f-a 
f-d 
f 
r-o 
Prunella vulgaris 
f-a 
f-a 
f-a 
0 
Stachys palustris 
— 
f-a 
— 
— 
S. arvensis 
— 
f 
f 
— 
Galeopsis Tetrahit 
f 
f 
f-a 
_ 
G. versicolor 
o-f 
— 
f 

Scleranthus annuus 
0 
a 
f 
a-d 
Polygomim Persicaria 
a-d 
f 
f-a 
f-a 
Rumex Acetosella 
d 
a 
a 
a-d 
Euphorbia exigua 
— 
0 
0 
r 
Aira caryophyllea 
s-o 
0 
0 
f-a 
A. praecox 
f 
0 
s 
f 
Bromus hordeacezes 
— 
r 
s 
f 
* These species, although most common on marshy pastures, have also been found on 
arable land. 
The behaviour of the following species is of particular interest. 
Spergula arvensis is seen to be by no means essentially a sand plant ; 
it may be abundant on all 4 sour ’ soils and dominant on clay and sand 
alike. Chrysanthemum s eg e turn is also distributed over ‘sour’ soils 
generally ; although rare on clays, it may be dominant on sticky loams and 
frequent on peat. Rumex Acetosella is most abundant on peat and sand. 
Potentilla Anserina and Gnaphalium uliginosum are both favoured by 
winter puddling ; the latter plant has been commonly found about gates, 
and near Greenhithe was the only plant on the floor of an orchard, on sand 
on which pigs had been kept all the winter. 
Scleranthus animus has also been found on all grades of ‘ sour ’ soil, 
even attaining to an abundant position on clay. Ranuncidus repens may 
completely overrun peat soils. 
It appears from a general consideration of the above table that the 
communities judged as a whole are more symptomatic of soil type than are 
the presence or absence of relatively few index plants ; and it must be 
