106 WEEDS OF FARM LAND 



it is a very conspicuous plant it can be removed by hoeing 

 or handpulling before the seeds ripen. 1 



Fool's parsley {&thu$a cynapium}. A considerable differ- 

 ence of opinion exists as to the toxic nature of this weed, but 

 there can be little doubt that it is decidedly poisonous. Stock 

 seem to refuse it and so rarely suffer by it, but humans have 

 been poisoned by using the leaves in mistake for parsley. In 

 some cases the consumption of the plant causes active poison- 

 ing, in others it is said to be harmless ; it is possible that this 

 contradiction may be due to the fact that the toxic principle 

 or alkaloid (coniine) varies in quantity according to the con- 

 ditions of climate and habitat under which the plant is grown, 

 or according to the stage of development in which the weed is 

 eaten. 2 Barthe 3 includes fool's parsley among the poisonous 

 Umbelliferae. 



Hemlock (Contum maculatum}. This plant has long been 

 famed for its poisonous qualities and is supposed to be the 

 source of the decoction drunk by Socrates. It is strongly 

 narcotic an^l causes paralysis and death. Probably hemlock 

 has caused more harm to human beings than to farm animals, 

 as the leaves have been mistaken for parsley, the roots for 

 parsnips, and the seeds have been used in error for anise. 4 

 Usually stock avoid it because of its strong fcetid odour, which 

 is especially marked when the plant is bruised. Goats seem 

 to be largely immune from the action of the poison, 5 which is 

 most abundant in the seeds but is also present in the stem and 

 leaves. The reports of the toxicity of hemlock vary from 

 different places, but according to Barthe 6 this increases as one 

 passes from cold to warm climates, and he states that in North 

 Europe it can be eaten without ill effects. Whenever possible 

 the plants should be pulled up and burnt and the ground kept 

 covered with other vegetation to prevent re-establishment by 

 seedlings. The seeds are said to be very short-lived and in 

 this way lose their vitality without the opportunity of germin- 

 ating. 



Horsetail (Equisetum spp^). Field horsetail (Equisetum 

 arvense) is the species usually met with on farms, but others 



1 A general description and discussion of the poisonous qualities of corn 

 cockle is given in Jour. Bd. Agric. (1910), XVII, pp. 38-45. 



2 Long, H. C. (1917), loc. cit., pp. 39-40. 



3 Barthe, L. (1918), " Toxicologie chimique," p. 499. 



4 Long, H. C. (1917), loc. cit., p. 41-42. 



5 Ewart, A. J. (1909), loc. cit., p. 29. 

 " Barthe, L. (1918), loc. cit., p. 499. 



