592 Angewandte Botanik. 



Brenchley, E. W,. The Weeds of Arable Land in relation 

 to the Soils on which they grow. (Ann. Bot. XXV. p. 155— 

 165. 1911.) 



Investigations have been carried out in Bedfordshire on 

 the soils derived from the Chalk, Gault, Lower Greensand, and 

 Oxford Clay, to determine the relations existing between the weeds, 

 soils and crops of arable land. The more important weeds are clas- 

 sified with their habitats and relative dominance, and particulars 

 are given as to the weeds of clay, chalk and sandy soils. The general 

 conclusions are summarised as follows: 



1. A definite association exists between the species of weeds 

 of arable lands and the soil on which they grow. The determining 

 factor is the actual texture of the soil, and not so much the geolo- 

 gical formation from which it is derived, except with soils over- 

 lying chalk. 



2. The crop has very little influence on the weeds occurring 

 except in the case of seed crops, which probably smother out a 

 number of species which would normally occur. 



3. Certain weeds are definitely symptomatic of particular types 

 of soil, though the majority of species are not so strictly circum- 

 scribed in distribution. Some species, also, are to be found indiscri- 

 minately on any soil. W. E. Brenchley. 



Brenchley, W. E., The Weeds of Arable Land in relation 

 to the Soils on which they grow. 2. (Ann. Bot. XXVI. p. 

 95—109. 1912.) 



The weed flora of parts of Wiltshire and Somersetshire 

 has been investigated with regard to the association between the 

 weeds and soils of the arable lands, the Upper Greensand, Chalk, 

 and Clay (Fuller's Earthj Coming under consideration. The comrao- 

 ner weeds are listed with their habitats and relative dominance, 

 and detailed accounts are given of the weed floras of the different 

 types of soils, special mention being made of "calcifuges". 



The conclusions arrived at are: 



1. In each district investigated a definite association exists be- 

 tween the species of weed plants and the soil on which they grow. 

 This association may be either: 



a. Local, when a weed is symptomatic of a certain soil in 

 one district but is not so exclusively associated with it in another. 



b. General, when a certain species is symptomatic or charac- 

 teristic of the same type of soil in different districts. 



2. In most cases there is no association between the weed and 

 the crop, though a few species do show a relationship. The weeds 

 usually found in "seed" crops seem to be constant, and certain 

 other plants exhibit the same association with particular types pf 

 crop in Bedfordshire and in the West Country. 



3. The relative prevalence of the weeds varies somewhat in the 

 different districts, certain species which are more or less common 

 in one place being practically absent in another, on similar soils. 



W. E Brenchley. 



Ausgegehen: 86 November lOlQ. 



Verlag von Gustav Fischer in Jena. 

 Buchdruckerei A. W. Sythoffin Leiden. 



