ELEMENTARY BOTANY 107 



others should be carefully studied by teachers where they 

 abound and introduced into their nature courses. Every 

 parent and child ought to know the dangers connected 

 with these plants, and the general study of them, as indi- 

 cated, would result in the saving of considerable suffering, 

 sickness, and death year by year. 



Poison Ivy, Rhus radicans. [Poison oak, three-leaved 

 ivy, mercury, black mercury, markweed, pikry (Me.).] 

 This is a common climbing, sometimes bushy, shrub 

 about roadsides and orchards. The stem has aerial roots 

 by which it clings. The leaves are compound with three 

 leaflets irregularly toothed and notched. They are bright 

 red when they appear in the spring, turn red again in the 

 fall, and are frequently gathered in children's bouquets. 

 The greenish flowers appear in May and June, and the 

 white waxy fruit remains through the winter. Through 

 ignorance it is sometimes even planted about houses. The 

 Bulletin says : " It is highly desirable that legal measures 

 be adopted compelling the destruction of these plants 

 where they abound in cities and in places of popular 

 resort." 



The poison is a heavy, gummy oil contained in all 

 parts of the plant and exuded from leaves, bark, and 

 fruit. This is very non-volatile and retains its virulence 

 unimpaired in old dry stems and leaves, which, therefore, 

 should always be promptly burned in destroying the 

 plants, and care taken not to inhale the smoke. Imper- 

 ceptible amounts, coming in contact with the skin, cause 

 the characteristic painful blisters. Such minute quantities 

 are effective that specially susceptible persons are some- 

 times affected by merely walking near the plants, when 



