130 



THE AMERICAN BOTANIST 



When latex is exposed to the air it soon coagulates, form- 

 ing a sticky, elastic mass, and its value in closing the breaks 

 in plant tissue are obvious, but the stories of its repelling 

 insects by being sticky are largely overdrawn. According to 

 Kerner, the ants are unable to climb the milkweed stalks because 

 their claws puncture the stems and the latex holds them fast, 

 but observation in the nearest milkweed patch will show plenty 

 of ant visitors in no way bothered by the latex. The sticky 

 latex may deter some insects from eating the foliage but others 

 do not appear to mind it. The latex of many plants contain 

 active poisons and these, of course, may protect the plants from 

 leaf eating animals of any kind. 



The many substances contained in the latex make it 

 frequently of use in medicine. Bloodroot and lobelia are valued 

 as emetics and expectorants, the argemone or prickly poppy, 

 and even the endive, is prescribed for jaundice, the juice of the 

 celandine is reputed to be a remedy against warts and the itch, 

 and the rattle-snake root is so named because its juice is 

 regarded as an antidote for snake bites. Opium, which is the 

 dried latex of the poppy, and medicines derived from it, are 

 said tO' be more frequently prescribed than any other drug. The 

 same substance, though in lessened quantity is found in the 

 juice of the common garden lettuce. It is possible that most of 

 the oyster-like flavor of the salsify and scorzonera are due to 

 the latex. 



In tropical lands, many trees and vines belonging to the 

 milkweed, fig, spurge, and dogbane families yield an abundant 

 latex containing caoutchouc. This being first brought from 

 India and used for erasing was known as India rubber or gum 

 elastic, but at present it is known simply as rubber. A poor 

 grade of rubber has even been extracted from our common 

 milkweed. Gutta percha, which is similar to rubber is also 

 derived from the latex of some species. 



