53 



other the skin irritation is plainly due to mechanical causes, as in the case 

 of Arctium and Xanthium. There seems to be no good reason why any 

 plant with piercing surface outgrowths, such as Biu'-grass (Cenchrus 

 tribuloides I..I. should not be included in the latter group and the list 

 almost indetinitely extended. Veiy little was done experimentally with 

 such plants, for though persistent and sometimes festering sores may 

 result from handling them, the irritation Is due to traumatic, uot to toxic, 

 causes. 



In the first group of plants an additional separation may be made into 

 those poisonous b.v mere handling and those whose poisonous properties 

 seem to be liberated only as the result of dry trituration or grinding, the 

 Avell known irritant effects of the dust arising from the dried roots of 

 Podophyllum being a case in point. 



It will thus be found that the number of plants which are really con- 

 tact poisons, under ordinary handling is A'try much reduced and the long 

 continued immunity of those of us who have collected widely is not after 

 all as wonderful as it might at tirst seem. As a matter of fact it would 

 seem that any plant, which in any way and under any conditions however 

 extraordinary produced a skin irritation had been promptly placed among 

 the contact poisons. There is also to be considered the personal idiosyn- 

 crasy. Some persons are peculiarly susceptible to plant poisons, either 

 because of an especially sensitive skin or of some constitutional condition 

 which makes them remarkably non-resistant to the sequelae of skin 

 lesions of any sort. As a result of this consideration of the personal equa- 

 tion the list of plants poisonous by contact is still further reduced. 



A rather careful experimental study of the plants in the above list has 

 been made with the following results: 



In all cases the procedure was simple but was deemed sufficient to 

 demonstrate the poisonous or non-poisonous character of the plant. The 

 plant was first handled freely in the way of collecting and making herb- 

 arium specimens. If after some da.vs no results were apparent, the part 

 of the plant said to contain the poisonous element was rubbed upon the 

 back of the forearm until serum, and at times blood, exuded, the .iuice of 

 the plant and the serum being allowed to dry upon the arm. If no results 

 followed, it was considered safe to infer that the form was not a contact 

 poison. 



Water plantain (Alisma Plantago-atiuatica Li. common throughout the 

 state in mud and shallow waters, is said by the National Dispensatory to 



