ii6 THE PLANT WORLD. 



The bark of this curious tree is said to be very rich in tannin and has 

 been exported for this purpose, although it is hardly probable to as- 

 sume much importance in this respect. 



The photograph from which our plate of the Elephant Tree was 

 made was taken by Mr. George P. Merrill on July 25th, 1892, at a 

 place called Tule Arroyo, about fifteen miles from the gulf coast. Its 

 use in the present connection is by the courtesy of the U. S. National 

 Museum. 



THE STINGING NETTLES. 

 By V. K. Chesmit, U. S. Department of Agriculture. 



THE Stinging Nettle {ilrtica dioica L.) is a stout, weedy peren- 

 nial, two to four feet high, with square stems, thin, heart- 

 shaped leaves, three to five inches long, and inconspicuous, 

 green axillary clusters of flowers and fruits. It is a native 

 of Europe, but has been extensively naturalized in the United States. 

 Among the other common names by which it is well known on this 

 continent are the following, viz: Nettle, Great Nettle, Great Stinging 

 Nettle, Common Nettle, Common Stinging Nettle. The plant grows 

 abundantly in waste places about dwellings throughout New England, 

 southwestward to Ohio and West Virginia ; less commonly southward 

 to Tennessee and South Carolina; somewhat rarely in Kansas and 

 Nebraska, but abundantly in the mountains of Colorado and Wyoming. 

 It is found in small quantity from Texas to California. 



The peculiar irritant property of this plant has been ascribed by 

 various chemists to formic acid, a glucoside, an alkaloid, and to a non- 

 volatile ferment. Formic acid alone does not produce the character- 

 istic effect. The alkaloid isolated by Oddi and Lomonaco (Rif. Med., 

 Apr., 1892,) is a crystalline compound and acts very powerfully on the 

 vaso-motor system. Whatever the nature of the principle may be, it 

 is certain that it exists mostly if not entirely in the glandular hairs 

 which, interspersed with two other kinds of hairs, sparsely cover the 

 whole surface of the plant except in the very early stages of its 

 growth. When brought into contact with the skin these glands inject 

 their poison into it, and an irritation is thus set up which is more or 

 less painful according to the susceptibility of the person and the num- 

 ber of hairs introduced into the skin. The itching is accompanied by 

 a more or less extended swelling or thickening of the skin. This be- 

 gins immediately and generally passes away in the course of a few 

 hours, but may last for a whole day. 



