VEGETABLE POISONS. 67 



sting. The last joint is formed just like the serpent's fang, 

 being hollow, having a sharp point with a slit near the end, 

 and a poison reservoir in the rounded base. When the 

 scorpion attacks an enemy, it strikes violently with the tail, 

 and the force of the blow drives out the poison just as is done 

 with the serpent's fang. 



At the bottom of the illustration is shown the poison-fang of 

 a Spider, which, as the reader may see, is formed just on the 

 principle of the scorpion-sting. 



NATURAL VEGETABLE POISONS. 



So much for animal poisons. We will now pass to the 

 vegetable world. 



Of the vegetable sting-bearers none are more familiar to us 

 than the Nettle, three species of which inhabit this country. 

 The two commonest are the Great Nettle ( Urtica dicecea) and the 

 Small Nettle (Urtica urens), and both of them are armed with 

 venomous stings, which cause the plants to be so much dreaded. 



The structure of these stings is very simple, and can be 

 made out with an ordinary microscope, or even a good pocket 

 lens. Each of these stings is, in fact, a rather elaborately con- 

 structed hair, hollow throughout its length, coming to a point 

 at the tip, and having the base swollen into a receptacle con- 

 taining the poisonous juice. When any object such, for 

 example, as the human hand touches a nettle, the points of 

 the stings slightly penetrate the skin, and the hair is pressed 

 downwards against the base, so that the poison is forced 

 through the hole 



One of these hairs is shown in the left-hand bottom corner 

 of the illustration. 



Even the tiny stings of our English nettles are sufficiently 

 venomous to cause considerable pain, and, in some cases, even 

 to aifect the whole nervous system. But some of the exotic 

 nettles are infinitely more formidable, and are, indeed, so 

 dangerous that, when they are grown in a botanical garden, 

 a fence is placed round them, so as to prevent visitors even 

 from touching a single leaf. 



The two most dreaded species are called Urtica heterophylla 

 and Urtica crenulata. The former is thought to be the more 

 dangerous of the two, and a good idea of its venomous qualities 



F2 



