422 SCIENCE PROGRESS 



soils are derived in succession from the geological series of 

 rocks comprising the Chalk, Gault, Lower Greensand and 

 Oxford Clay ; in Wiltshire, where the Chalk again reappears ; 

 and in Somerset to the south of Bath, on the heavy calcareous 

 clay land overlying the Great Oolite, Fuller's Earth, Lower 

 Oolite and the Lower Lias. 1 



In examining the results arrived at, it must be remembered 

 that so far only a limited area comprising soils derived from 

 very few geological series has been investigated and that until 

 the work has been extended over wider areas, so as to embrace 

 more numerous geological formations and also to include the 

 same formation in different parts of the country, the conclusions 

 must necessarily be recognised as being largely provisional and 

 subject to modification. 



Care has to be taken in this selection of districts to be 

 examined. In some parts of the country, e.g. Norfolk and 

 Suffolk, 2 the soil is not derived directly from the underlying 

 rocks but is formed from drift that has been carried from other 

 regions and deposited by glacial action ; for the purposes of 

 the immediate investigation such soils are disregarded, attention 

 being confined to those that are as far as possible free from 

 drift, so that the connection of the underlying rock with the 

 weed flora can be more easily determined. The plan adopted 

 is to visit as many as possible of the farms scattered over the 

 area under investigation, during the summer months, from about 

 the end of May, when the weeds are beginning to make pro- 

 gress, up to the beginning of harvest time. The fields are 

 thoroughly traversed and searched, every species of weed 

 occurring in each field being noted, as well as the nature of 

 the soil and the crop grown ; the relative prevalence of each weed 

 is also indicated, the classification being into (i) dominant, (2) sub- 

 dominant, (3) distributed, (4) occasional and (5) scarce or rare. 



The distinction between the weeds growing actually with 

 the crop and those in the adjoining hedgerows has been found 

 usually to be very sharply marked ; a few plants are common 

 to both habitats but on the whole the hedgerow plants appear 

 to have been unable to enlarge their borders by spreading into 



1 W. G. Brenchley, " The Weeds of Arable Land in Relation to the Soils in 

 which they Grow " (II.), Ann. Bot. January 19 12. 



2 F. W. Harmer, " Glacial Deposits of Norfolk and Suffolk," Trans, Norfolk 

 and Norwich Nat, Soc. ix. 19 10. 



