ARABLE WEEDS. ASSOCIATION WITH SOILS 131 



(c) Plants Occurring on all Soils, but less Frequently on 

 Chalk. The weeds in this category show a regular gradation 

 of frequency. 



(1) Plants that are merely less common on chalky soils, 

 such as Veronica hedertzfolia and Veronica arvensis. 



(2) Plants that are so much less common on chalk that a 

 dislike of such soil is suggested, as Alchemilla arvensis, Laininm 

 piirpureuin, Matricaria chamomilla, Matricaria inodora, and Poa 

 annua. 



(3) Plants which are so infrequent on chalk that a dislike 

 of calcareous soil is evident, as Papaver argemone, Polygonuui 

 persecaria, Rumex obtusifolius. 



TABLE III. WEEDS OCCURRING ON ALL SOILS, BUT LESS FRE- 

 QUENTLY ON CHALK. 



(i) Ivy-leaved speedwell (Veronica hederafolia} is of fre- 

 quent occurrence and is often dominant. The plant is of a 

 very early and ephemeral habit, and as soon as growth is 

 completed it ripens its seeds and dies off rapidly, so that in 

 many cases by the end of June few traces of an abundance of 

 plants are to be seen. Consequently, it may easily happen 

 that if fields are examined late in the season the speedwell 

 may be missed in areas in which it dominates at an earlier date. 

 It seems to be equally dominant on all types of soil, as even 

 on chalk it maintains its position in this respect, although the 

 plant is so much less frequently seen in this situation. 



Wall speedwell ( Veronica arvensis} is much less common 



9* 



