182 



THE CASHEW FAMILY ANACARDIACEAE. 



This family contains a large number of small trees and shrubs 

 and a few woody climbers widely distributed over the world, but 

 most abundant in the tropics. Many of the representatives of this 

 family are noted for their acrid, resinous, or milky juice which makes 

 th,em of considerable value in medicine, tanning, and the manufac- 

 ture of varnishes and resins. 



About 50 genera with 500 species belong to this family. North 

 America has few representatives. Only 3 genera with tree repre- 

 sentatives are embraced in its flora. The genus Rhus is the only one 

 native to northeastern America. It has representatives in Pennsyl- 

 vania. 



THE SUMACHS RHUS, Linnaeus. 



The Sumachs comprise a large number of trees and shrubs which 

 are widely distributed. About 120 species are known of which num- 

 ber about 16 species are native to North America and 6 to Pennsylva- 

 nia. Most of the species of this genus are found in South Africa. 

 All have large pithy twigs and a milky, sometimes poisonous, sticky 

 juice. The leaves of all are alternate. One species alone is ever- 

 green and one other has simple leaves. All others are deciduous and 

 have compound leaves. 



Three of the 6 species native to Pennsylvania reach tree-size. The 

 others are mere shrubs. The Poison Ivy or Poison Oak (Rhus Toxi- 

 codendron L.) is very abundant along fences and by roadsides. Its 

 stem often trails along the ground and sends up short branchlets 

 which bear the compound leaves with 3 leaflets. The leaves are 

 poisonous to the touch. The Smooth Sumach (Rhus glabra L.) 

 is a low-growing and spreading shrub sometimes becoming a small 

 tree. It has glabrous branchlets which are more or less glaucous. 

 It has compound leaves with 11-31 leaflets. It is very common in 

 abandoned fields and seems to thrive on sandy soil. The Fragrant 

 Sumach (Rhus canadensis Marsh.) reaches a height of 2-6 ft. It 

 has compound leaves with 3 leaflets which are aromatic when crushed. 

 The Smoke-Tree (Rhus Cotinus L.) is one of the commonest 

 plants of our gardens and lawns. It is an introduced species com- 

 ing from Europe and warm-temperate Asia. Locally it has escaped 

 cultivation. 



