164 Brenchley . — The Weeds of Arable Land in relation to 
Triticum repens 
Tussilago Farfara 
Veronica arvensis 
„ hederaefolia 
Veronica agrestis 
It should be noted that while Poa annua , Plantago major , and Ranun- 
culus arvensis are absent from seed crops, other species of the same genera, 
e. g. Poa trivialis , Plantago lanceolata y and Ranunculus acris . are very frequent 
in such surroundings. While the variety of crop does not greatly influence 
the weed flora, still the cultivation frequently affects the prevalence of cer- 
tain weeds the following year. 
a. Care was taken to discover the various species of plants designated 
as * Twitch ’ in the different localities. Any grass which runs along the sur- 
face of the soil or covers it to any great extent is apparently so called, the 
following species being included under this heading : — 
Agrostis stolonifera Phleum pratense (var. stolonifera) 
Alopecurus agrestis Poa annua 
Lolium perenne Triticum repens 
3. Special investigations were made to determine whether Coltsfoot and 
Equisetum , which so often occur in company, are in any way characteristic 
of some particular quality of soil. Samples of the soil were tested with 
litmus for acidity and hydrochloric acid for alkalinity, with the result that 
both species were found to occur indiscriminately, and so could not be 
regarded as indicative or symptomatic. 
Spergida arvensis , 4 spurry/ on the other hand, is very symptomatic 
of acid soils, and it disappears entirely where lime is applied, reducing the 
acidity. Lime also kills out Mayweed in many cases. 
4. ‘ Mayweed 5 ( Matricaria sp. and Anthemis sp.) seems to be very 
impatient of competition. If the crop is in any way heavy little or no 
Mayweed is to be found among it, though it occurs in enormous quantities 
round the edge of the fields, along lines of drainage, and wherever there may 
be a clearing in the crop. 
Ftimaria officinalis does not generally occur in any great abundance, 
but occasionally it is so prevalent on chalk that it is necessary to hand 
cultivate to get rid of it in order to save the crop. This is notably the 
case in the Maiden’s Bower, an old Roman encampment near Dunstable. 
Allium vineale was only met with in one locality on the very heaviest 
of clay land. This weed reproduces itself by offsets, bulbils, and seeds, and 
its vitality is so great that no known method of cultivation seems competent 
to eradicate it. 
