368 
Agricultural Weeds. 
Iiifluence of Soil upon Weeds. — The effect of soil upon the 
growth of all plants is a matter which is perfectly familiar to 
every one. It is from this cause that, when wild land is brought 
into cultivation, its natural plants change. Chichicccd, sandworts, 
groundsel, spurge, and dead-nettles, are nowhere found in un- 
broken ground, but in land newly brought under tillage they 
soon make their appearance. 
But however much land may be tilled in one district, we have 
in it a different wild flora from that in another — the staple 
commodity of the soil, whether of sand, lime, or clay, exerting 
considerable influence. Viewed in this light, the observation of 
common weeds may be made valuable, as indicating the kind of 
soil, and leading us to infer different degrees of barrenness and 
fertility. Our table shows that clay or heavy land is subject to 
the fewest species of weeds ; and this is found to coincide with 
everyday observation. If we examine the shales of the Silurian 
rocks, the clays and shales of the lias, the fuller's earth clay, or 
the Oxford clay, where these are unmitigated, we shall not only 
find small cultivated crops, but also few species of weeds, and 
even these for the most part flourish but badly ; indeed, clays in 
general are inimical to rich vegetation, both from their mecha- 
nical texture and chemical composition ; * the common term 
" hungry clay " is expressive of its being without the food re- 
quired by plants. 
Next to clays we would instance sandy or silicious soils as 
producing a scanty vegetation, both as regards crop and weeds ; 
at the same time there are some species which flourish only on 
sands ; and the beautiful appearance (as far as colour is con- 
cerned) which is given to a sandy corn-field by the red poppy 
and the bluebottle could not fail to excite the attention of those 
who may have seen them growing on the tertiary sands of Suffolk, 
or on the deep sand-beds which till up the lias basins about Chel- 
tenham and Gloucester, the limits of which in all cases are most 
accurately defined by an abundance of wall barley. 
Calcareous soils for the most part have a very distinctive 
natural vegetation, and even in cultivation many of its character- 
istic wild plants cling to it most perseveringly. Mountain lime- 
* This requires qualification. Clays that are imperfectly drained and badly 
farmed doubtless produce the scanty vegetation here described, and may not 
inaptly be termed " hungry " in the sense of being deprived of their proper support, 
whether derived from the atmosphere or the farm-yard. The chemical consti- 
tution, however, of most clays, is well adapted for the support of vegetable life, 
and it should be the farmer's business to alter the mechanical texture, which is the 
chief cause of barrenness on such soils. I have never yet seen clay thoroughlj- 
drained, deeply cultivated, and reasonably well farmed, which did not speedily 
lose the name of hungry/, and earn the title of grateful clatj. — H. S. Thompson. 
