AMCARDIACEAE 



handsome ornamental. 



* Rhus r ydborgii , Poison Oak, is widely distributed in the 

 Rocky Mountains • It is similar to the Poison Oak of the east and 

 the Pacific Coast states. Its sprawling habit where it does not 

 have trocs to climb makes it ideal for erosion control in moist 

 bottoms of oanyons. Its use of course cannot be advocated. If 

 the economic importance of the Poison Oak and Poison Ivies could 

 be accurately computed it would doubtless run into the millions in 

 the United States ever;/ year, on the debit side. The fi-rst cost 

 is in medicine and doctor bills which the United States over is 

 enormous; the next is in lost time which is doubtless much greater. 



CELASTRACEAE 



Murto nia s cabrella . The traveler in the southwest who visits 

 the old mining town of Tombstone, Arizona, is likely to become 

 curious regarding a shrub which is very abundant on the rocky slopes 

 in that region. This shrub is stiffly erect and has curious, very 

 thick, hard oval leaves. In fact the leaves look like little pieces 

 of leather with rolled edges. They are grayish green. This shrub 

 is confined in our range to southern Arizona. It is valueless as 

 forage but owing to its abundance does play a worthy part in binding 

 the soil. 



Canotia hclac a ntha is sometimes called Crucifixion Thorn al- 

 though it is a very different plant from the Crucifixion Thorn of 

 Palestine. This term is also applied to two other southwestern 

 plants, each representing a distinct family of plants. As the com- 

 mon name implies, the plant is a macs of thorns. These in common 

 with the stems, are green. There are no leaves. The plant is a 

 large shrub or small tree of erect habit. It has been reported from 

 a limited area in southern California but is most common in central 

 Arizona where it forms forests of limited extent. Growing as it 

 does in very rough, rocky slopes of rather loose soil, it is a good 

 soil binder. Owing to the fact that the plants are utterly useless 

 for browse and of little value as fuel, no attempt has been made to 

 propagate the species in the nursery. 



Pachystima myrsin ites , Uyrtle Boxlcaf, is a low shrub found 

 in the high forests throughout the west. It has beautiful small, 

 shiny lea\ r es and inconspicuous flowers. It is a good erosion con- 

 trol plant in regions whore erosion control is not a problem. It 

 is totally un suited to arid regions or low altitudes. 



ACEPACEAE 



Acer negundo or common Box Elder, is widely distributed in 

 Region 3 as well as elsewhere in the west. It is reasonably drought 



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