6 Introduction [CH. 
shown the average of thirty samples of foreign root to be 0-3 per cent. 
It is interesting to observe that the average of nine samples of root 
grown at Darenth is 0-54 per cent. In order to determine whether 
this variation was due to collecting at different times of the year, roots 
from the same plot, derived from second year's plants, which were sown 
at the same time, were dug up at intervals and dried. The following is 
a record of the analysis of these samples : 
March, 1911 0-56 per cent- 
May, 1911 0-59 
June, 1911 0-53 
August, 1911 0-50 
December, 1911 0-59 
" The amount of variation throughout the year is thus seen to be very 
small." 
Dunstan (Bui. Imp. Inst., 1905) has shown that Hyoscyamus muticus 
grown in India yielded 0-3 to O4 per cent, of hyoscyamine, but that 
the same species grown in Egypt produced 0-6 to 1-2 per cent. 
According to Esser no coniine is found in Conium maculatum growing 
in the far north. The same authority says that the root of Hyoscyamus 
niger is quite free from toxic properties in winter. 
Variation in the Poisonous Parts of Plants. As will be shown 
in succeeding chapters, many plants (e.g. meadow saffron) are poisonous 
in all their parts, though the amount of the toxic substance may differ 
according as to whether the seeds, leaves, stem or roots are severally 
considered. In other cases one part of the plant alone is toxic (e.g. the 
seeds, as in corn cockle). Further, some species vary in the percentage 
of the toxic substance in the leaves before and after flowering. 
Frequently the root is the most toxic portion of the plant. This point 
may be usefully recollected in relation to poisoning of live stock, which 
are in general affected by the foliage or ripe seeds. 
Eradication of Poisonous Plants. Wherever poisonous plants are 
found, particularly in quantity, where they are liable to be eaten by 
live stock, an attempt should be made to eradicate them. They may 
be simply dealt with as weeds as may be necessary according to the 
species concerned. When any difficulty is experienced in regard either 
to determination of the species or to methods of eradication the advice 
of the Board of Agriculture and Fisheries (Whitehall Place, London, 
S.W.) should be requested. Stock should at once be removed from 
a suspected pasture, which should be immediately and thoroughly 
