This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
Other Common Names: Poison, White or Bearded Darnel, Tares.
The history of Darnel is interesting. The plant has been known and its ill effects noticed for hundreds of years. It is believed to be identical with the tares of Scripture. The seed, being of approximately the same size as the grain, had to be separated by hand, the women performing this tedious task on the flat housetops.
There are many cases where people have been badly poisoned by eating Darnel in bread or meal, but few if any deaths are recorded. This is not true of the lower animals, many of which have been killed by eating it in ground feeds. Pigs, horses and sheep have suffered most. At the Lyons Veterinary School a horse was fed 4.4 lbs. of the seed and died as a result. Cornevin states that Darnel in the proportion of 0.7% of the weight of a horse will produce death, while 1.5 to 1.8% is required to produce the same result in ruminants and poultry.
The seeds only are poisonous, their effect being due to the presence of the alkaloid temulin, of which they contain, according to reputable analysts, 0.6% by weight. In the fruits of some 70% to 80% of the plants is a fungus which lives sym-biotically with the plant, and is supposed by many to cause the trouble. This fungus forms a layer of hyphae just outside the aleurone layer of the grain. It has never been observed to produce fruiting bodies or spores, and its relationship is not known. As the seed sprouts the fungus keeps pace with the growth of the young plant, and finally affects the grain again. Feeding tests which would prove whether the fungus is responsible for the poisoning have not been made.
Fig. 19. - Grains of Darnel - Lolium temulentum. Five times natural size.
The symptoms are those of a deliriant nerve poison. There is confusion of sight which was known in very early times and is mentioned by classic writers. Further symptoms are dilation of pupils, giddiness, drowsiness, staggering and stupefaction. Trembling is followed in some cases by convulsions. In others vomiting and purging may take place. The respiration is laboured and the pulse slow. Inflammation of stomach and intestine have been observed.
The plant was introduced from Europe. It is most plentiful along the eastern and western coasts, but is found locally in the interior, growing in waste places and among grain crops. It is an annual grass from two to four feet high, with a smooth, stout stem, and rather broad leaves, rough above. The spikelets, each containing four to eight seeds, are arranged alternately, pressing into slight curves in the rachis, or main stalk. The fruit, which alone produces trouble, is not unlike a small grain of barley in appearance. The hulls enclose the kernel very tightly, the outer one being hard and flinty, and the inner minutely bristly along the edges. The size is about that of a small grain of wheat.
The Plant and Seed