Agricultural Weeds. 
369 
stone, oolitic limestone, chalk, and marls, have a distinctive weed 
iiora in such plants as viper's bugloss, gromwell, ragwort, hard- 
head, wild parsnep, scabious, succory, and others. Indeed, no 
soils are more prolific of species of weeds than those of a calca- 
reous nature ; and there can be but little doubt that many of the 
plants tliat we have tabulated under the head of loam are only 
found there from the circumstance that all good agricultural 
loams contain more or less lime. 
In the list of weeds which are denizens of loamy soils will be 
found for the most part the true agrarians, such as chickweed, 
groundsel, the speedwells, mustards, and goosefoot, all of which 
most pei'severingly track cultivation. Now, as loams — by which 
we mean good soils — are adapted to the growth of our cultivated 
crops from the ciixumstance that their mechanical structure 
and chemical ingredients are such as crops require for their 
increase, it is no wonder that such soils should also offer a large 
list of weeds ; and as in such positions weeds, like the crop, 
perfect all their parts, and bring forth a quantity of seed which 
appears to be remarkably fertile, we may not wonder that, al- 
though there is a constant warfare against weeds in cultivated 
districts, yet, from the defective modes in which this is too often 
carried on, they sometimes spread in a most unexpected and 
unlooked-for manner. 
But there appears to be a most important point connected 
with agrarian weeds, that has been, if not overlooked, at least 
much neglected, and this mainly from the want of more analyses 
of weeds, namely, that weeds common to good cultivated soil 
appear to possess some of the most important chemical principles 
in great quantities. Hence weeds are a twofold nuisance, as they 
not only appropriate valuable space, but live upon the fat of the 
land — both, of course, to the prejudice of the cultivated tribes. 
This fact will appear obvious from Table II. (p. 370), repre- 
senting the results of ash analyses of some of our common 
weeds. 
For the results of 1, 2, and 3, in this table, I am indebted to 
the kindness of my friend Dr. J. Blyth, Professor of Chemistry, 
Queen's College, Cork. These analyses, to the limited extent 
to which they have been carried, show that the alkalies and 
phosphates are abundant in agrarian weeds, which is just what 
we should expect from our experience of the injury inflicted by 
them on our cultivated crops. They show us further that allow- 
ing such weeds to seed not only causes a perpetuation of their 
evil consequences, but also tends, in a still larger measure, to the 
abstraction of some of the most valuable food of plants, especially 
the phosphates. 
