ARABLE WEEDS. ASSOCIATION WITH SOILS 145 



arable land it is a characteristic feature on sandy and gravelly 

 heaths and commons where lime is lacking from the soil. 



Corn marigold (Chrysanthemum segetum) (Fig. 39) is 

 shrouded in a 

 slight air of mys- 

 tery. Obviously 

 enough sandy 

 soils are con- 

 genial to it, as it 

 usually occurs in 

 such situations 

 and is relatively 

 often dominant 

 there, whereas 

 Buckman l states 

 that it is an index 

 of rich soil. But 

 the weed is by no 

 means common, 

 being very local, 

 and even in the 

 same district it is 

 localised to cer- 

 tain fields. It is 

 evident that some 

 other factor, in 

 addition to lime 

 deficiency and 

 soil texture, de- 

 termines its dis- 

 tribution, and it 

 seems possible 

 that this factor 

 may be that of 

 moisture. A 

 comparison of 

 the number of 

 occurrences with 

 the number of ^ IG ' 39* CORN MARIGOLD (Chrysanthemum segetum). 



times it is dominant suggests that the plant is ultra-particular 

 as to its habitat and is most intolerant of any untoward cir- 

 cumstance, but that when its peculiar needs are met it is 



1 Buckman (1855), your. Roy. Ag. Soc., XVI, p. 363. 



10 



