POISONING BY PLANTS. GENERAL PRINCIPLES 13 



influence this variation. The following are some of the reasons for this 

 difference in the amount and activity of the poison derived from' the same 

 species of plant. 



1. Glucoside Transformation. It has been found that in some plants 

 the poisonous substance does not exist in the plants themselves, but 

 appears only when one substance in the plant comes in contact with and 

 is acted upon by another substance which may be called the activator. 

 This is illustrated in the leaves of the wild black cherry, Prunus serotina, 

 which do not contain any active poison until they become dried, when its 

 glucoside substance, probably amygdalin, is acted upon by emulsin, 

 an enzyme, and converted into the poisonous hydrocyanic, or prussic acid. 



2. Influence of Age of Plant The age of the plant materially influ- 

 ences the virulence and the amount of poison present in the plant. Some- 

 times a young plant is more actively poisonous than an old plant and vice 

 versa. The death camas, Zygadenus venenosus, native of Montana and 

 other western states is more poisonous before it comes into bloom. On 

 the other hand, the seeds of the lupines (Lupinus) are the only parts of the 

 plants positively known to be poisonous. 



3. Character of Organ. Different organs of the same plant vary as to 

 their content of poison. Some parts are inert, others are deleterious. 

 The green leaves and stems of the common potato, Solanum tuberosum, 

 are poisonous, especially when wilted, while the tubers form an everyday 

 article of diet. The fruits of spotted cowbane, Conium maculatum 

 and the seeds of Datura Stramonium, the thorn apple, are more poisonous 

 than the foliage. 



4. Seasonal Variation Poisons. There is a considerable variation in 

 the amount of poisonous material produced in plants from season to season. 

 Thus the mature bulbs of Colchicum contain a much larger amount of 

 toxic substance than the growing bulbs. Miss Alice Henkel in a paper 

 on "American Root Drugs" notes that the roots of the American 

 hellebore, Verairum viride, should be collected in the autumn after the 

 leaves are dead. 



5. Influence of Climate. Climate has a marked influence on the 

 development of poisonous substances in plants. Dunstan has shown 

 (Bui. Imp. Inst. 1905) that Hyoscyamus muticus grown in India yielded 

 0.3 to 0.4 per cent, of hyoscyamin,but that the same species grown in Egypt 

 produced 0.6 to 1.2 per cent. Esser states that no coniin is found in the 

 spotted cowbane, Conium maculatum, in the far north. 



