74 



CIVIC BIOLOGY 



iMucli suffering is caused by poison ivy, the active poison 

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

 the dried Avood. The oil is soluble hi alcohol and may be 

 removed from tlie skin by tlioroughly bathing exposed parts 

 in alcohol and then washing off with water. An alcoholic 



Fig. 34. Purple or woolly loco weed — Astragalus mollissimus 



Photograph ))y C. D wight ISIarsh, 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. 



Aduitioxal Studies 



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

 roads, in grass, field, back^^ard, and garden. 



2. Compare number of seeds borne by a w^eed with those of a wheat, 

 oat, or barley plant. 



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



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

 animals to their advantage ? 



