6 



Introduction 



[oh. 



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 

 May, 1911 .. 

 June, 1911 . . 

 August, 1911 

 December, 1911 



0-56 per cent. 

 0-59 „ „ 

 0-53 „ „ 

 0-50 „ „ 

 0-59 „ „ 



" The amount of variation throughout the year is thus seen to be very 

 small." 



Dunstan {Bui. Imp. Inst., 1905) has shown that Eyoscyamus muticus 

 grown in India yielded 0-3 to 0'4 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 Hable 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 difl&culty 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 



