DEFENCE. lOI 



prescribed way. They are shut or open according to 

 the degree of tightness or expansion of the watery 

 tissues below them. When this is full of moisture they 

 open, but close when it becomes dried through the 

 escape of water. The lenticels are small, rough, lip-like 

 protuberances easily seen on the twigs of most trees. 



Latex. — Another defensive arrangement is found in 

 the Latex or Milky juice, which occurs in the rind or 

 cortex of many plants, though unfortunately it is by no 

 means common. This Latex is a complex mixture of 

 indiarubber, guttapercha, resins, oils, proteids, and 

 occasionally starch. It occurs in long branching tubes 

 or cells which run up and down the plant, especially in 

 the bark or cortex of the stem, though the tubes are 

 also found in other parts. The substance is very 

 elastic. It is very resistant to fungi, and is also water- 

 proof. It generally contains bitter substances, often of 

 a very poisonous nature ; thus opium, laudanum, and 

 morphia are made from the latex of the poppy. The 

 milky juice of the tree Euphorbias found in East Africa, 

 is said to produce blindness if it touches the eyes, and 

 certainly raises painful blisters on the skin. These 

 rubber-bearing trees are especially common in Brazil, 

 along the Amazon and its tributaries. In this region, 

 there are many wood-boring insects which eat through 

 the bark, and, of course, are apt to injure the trees. If 

 such a beetle is met by a gush of milky latex, it will 

 certainly either be overwhelmed and destroyed, or at 

 any rate it will be unable to continue its attack. As 

 the rubber coagulates and forms a sort of rubber-stopper 

 over any wound in the bark, it must be a valuable 

 protection against such enemies. 



Mr. Belt in his Naturalist in Nicaragua mentions 

 that trees which had been drained of their latex by too 



