350 PLANT-LIFE 



necessary to carry. It would seem that these little 

 mites emerge from their shelter during the night, and 

 pounce upon bacteria or such spores of algae, lichens, 

 and fungi as happen to settle in their neighbourhood. 

 Apparently the mites pay for the shelter given by the 

 leaves by protecting them from the attacks of very 

 subtle foes. A tiny insect, Cynips argentea, produces 

 peculiar galls on the Oak (Quercus pubescens) . It chances 

 that these galls secrete honey. Ants are attracted by 

 the honey, and render valuable service to the tree by 

 warding off predatory snails and larvae. The reader 

 will hardly need to be reminded that such protection as 

 is afforded in this remarkable case is accidental, not 

 designed. The insect happens to find a vulnerable 

 point in the plant, and a gall results ; the secretion of the 

 honey is the result of peculiar stimulation; the ants are 

 attracted by the honey, and they chance to serve the 

 plant by their warlike attitude to certain of its enemies. 



