74 CIVIC BIOLOGY 



Much suffering is caused by poison ivy, the active poison 

 being a nonvolatile oil found in all parts of the plant even 

 the dried wood. The oil is soluble in alcohol and may be 

 removed from the skin by thoroughly bathing exposed parts 

 in alcohol and then washing off with water. An alcoholic 



FIG. 34. Purple or woolly loco weed Astragalus mollissimus 



Photograph by C. Dwight Marsh, United States Department of Agriculture, 



Bulletin 112 



solution of sugar of lead (lead acetate) destroys the oil. The 

 same remedy applies to poison sumac and poison oak. 



ADDITIONAL STUDIES 



1. Prepare a list of common weeds found along the roadside, rail- 

 reads, in grass, field, backyard, and garden. 



2. Compare number of seeds borne by a weed with those of a wheat, 

 oat, or barley plant. 



3. What weeds do you know that are eaten as vegetables ? 



4. How is the fact that weeds are not valuable food for domestic 

 animals to their advantage ? 



