FLOWEBING PLAXTS AND FERNS OF INDIANA. 579 



fectly innocuous to most persons may prove poisonous to the few who 

 are peculiarly susceptible to plant poisons. A familiar illustration is 

 furnished in the case of the foliage leaves of our ordinary tomato, 

 which most persons handle with impunity, but which in many re- 

 corded cases have proved a serious skin poison. As a rule, this suscep- 

 tibility to contact poisoning can only be discovered through experi- 

 ence, but persons poisoning easily upon contact with the more virulent 

 plants of this type should handle with care certain plants that are 

 considered harmless. 



PLAXTS POISONOUS BY CONTACT. 



This list is very properly headed by the well known Poison Ivy or 

 Poison Oak (Rhus radicans). Because of its wide distribution and its 

 various habits of growth, it is probably properly chargeable with a 

 Jarge proportion of the cases of plant poisoning. In most regions of 

 the State it is found as a climber, ascending trees, in- some places it 

 trails over rocks by means of rootlets, in others it is a low, erect shrub. 

 It may be readily recognized by its three ovate, sharp-pointed leaflets, 

 the terminal or middle one being wedge shaped at the base. The 

 margins of the leaflets are irregularly wavy or variously notched 

 scarcely any two being alike. The under surface of the leaflets is 

 usually somewhat downy. The poisonous principle in the plant is a 

 heavy oil and not a volatile substance, as is generally supposed. It is 

 found in all portions of the plant, though perhaps in greater amount 

 m the leaves than elsewhere. The oil is soluble in alcohol but not in 

 water. In cases, therefore, where there is fear that the plant has been 

 touched, the hands should be thoroughly washed in strong alcohol as 

 soon as possible. The wide distribution of the poison ivy is, in some 

 measure, due to crows, these birds being especially fond of the fruit. 

 The seeds are ejected uninjured and are thus spread over the large 

 areas which the crow covers in his search for food. 



More virulent in its action than the poison ivy is the "Poison Elder 

 or Dogwoods Its more restricted range, however, being confined to 

 swamps, makes it much less dangerous than the former. Many per- 

 sons who are immune to poison ivy are poisoned severelv upon contact 

 with the poison elder. In habit the plant is a shrub,' ranging from 

 eight to twenty feet in height, bearing large, compound leaves, some- 

 what resembling those of the alder, of from seven to thirteen leaflets 

 The poisonous principle is probably of the same character as that of 

 the poison ivy, although it has not yet been satisfactory worked out. 

 Botanically, the plant is known as Rhus vernix. 



