152 WEEDS OF FARM LAND 



field. In addition to these fat hen (Chenopodium album}, black 

 bindweed (Polygonum convolvulus), and field pansy ( Viola 

 tricolor] occur frequently in greater or less abundance. The 

 other species found are less characteristic of peat soils and 

 are more erratic in their distribution. An analysis of the 

 weeds seen on twelve fields on Eyerton Carr on 28th June, 

 1915, may be of interest, as the list (see page 151) shows 

 very clearly how severely the personnel of the weed flora is 

 limited by the habitat. 



COMPARISON OF DISTRIBUTION OF ARABLE WEEDS AS 

 RECORDED BY VARIOUS OBSERVERS. 



It is instructive to compare the absolute quantitative results 

 obtained by the Rothamsted methods of working with the 

 more empirical results set forth by other workers from records 

 of practical experience and accumulated general observations. 

 Two convenient lists are available, given by Buckman 1 (1855) 

 and Long 2 (1910). 



A close comparison of the habitats of the various weeds as 

 given by the three sets of observations shows most remarkable 

 agreement. This agreement is absolute, except with regard to 

 some thirty-seven species, and with these the discrepancy 

 is usually slight and due to the fact that one or other investi- 

 gator has made a closer association of the weed in question 

 with some particular soil. This may easily happen, as local 

 variations in distribution are bound to influence the judgment 

 of the worker to some extent. For instance, Long and Buck- 

 man associate Euphorbia exigua with loams, whereas the 

 writer finds it on all types of soil, with some preference for 

 heavier land. Again, Long associates Scabiosa arvensis with 

 all soils indifferently. Buckman confines it to calcareous land, 

 whereas the writer finds it on all soils, with a preference for 

 chalk, thus reconciling the opinions of the other two authorities. 

 Similar reconciliations can be effected in most instances where 

 discrepancy exists, and the only cases in which the variations 

 in the lists are significant are given in the following table, any 

 result which is seriously disputed being put into italics : 



1 Buckman (1855), "On Agricultural Weeds," Jour. Roy. Agric. Soc., XVI, 



PP- 359-367- 



2 Long, H. C. (1910), " Common Weeds of the Farm and Garden," pp. 

 384-408. 



