142 RESUME. 



oat, various grasses, geraniums, the rose, the larch, and 

 doubtless many other plants. 



(10.) The excessive appearance of any particular insect 

 is no new fact, but has been before noticed in the locust, 

 various caterpillars, the cockchafer, and in many other 

 instances. 



(11.) The excessive increase of one species of Aphis is 

 generally attended with a corresponding increase in other 

 species, so that human food may be attacked at all points. 



(12.) Aphides are kept in subjection by ichneumons and 

 other Hymenoptera ; by various Coleoptera, as lady-birds ; 

 by some dipterous insects, and by spiders, birds, &c. 



(13.) According to analogy the disease is doubtless 

 transitory, and will pass over the globe and disappear. It 

 may, however, yet increase^ and kill millions from famine 

 before it finally departs. 



(14.) A diseased potatoe may grow a diseased potatoe, 

 and thus propagate the malady ; although it is also pretty 

 certain, that a rotten potatoe, under certain circumstances, 

 may grow a sound one. 



(15.) We do not observe the effects of the disease to such 

 an extent in those plants which we employ before they are 

 required to develope their fibre, and therefore before they 

 exhibit the gangrene to any very great extent. 



(16.) The disease may probably be lessened by striking 

 at the cause, and destroying the Aphis to as great an extent 

 as possible by employing birds for that purpose, by burn- 

 ing infected haulms, and isolating from each other all plants 

 liable to be affected by the insect. 



(17.) A diseased plant may possibly be rendered less 

 liable in future to the disease, by causing it for some time 

 to revert as much as possible to the wild state, which is to be 



