TREE BLIGHT. 357 



field of scientific research, which it would be totally 

 impossible to do more than merely hint at here ; never- 

 theless, under other names as we venture, rightly or 

 wrongly, to believe, these things are all merely modi- 

 fications of the same natural law, affecting the various 

 orders of animated beings, which even descends to 

 govern the operations of the germs themselves (for 

 we know that the " vis medicatrix Naturae, " is in general 

 curing its own diseases) by a pestilence, or sudden 

 and various forms of death, among the micro-organisms 

 themselves. This is splendidly illustrated in the 

 vegetable world, where "blight," the effect of count- 

 less myriads of minute organisms, preying upon the 

 tree or plant, suddenly disappears, and from no apparent 

 discoverable cause, become as though it had never 

 been. What is this, but a tremendous pestilence sweeping 

 away these innumerable parasites? Let us quote as a 

 specific instance of this the great blight recently 

 affecting the silver fir trees (Picea Pectinata], in 

 many parts of Great Britain. We had occasion to pay 

 great attention to this, to try to devise some remedy, 

 to combat the fell disease that was destroying these 

 beautiful and valuable trees. We saw a promising 

 young plantation whose stems and branches were 

 literally covered with a white mildew (apparently) 

 these were all insects. * We came back next year 

 in the autumn time to observe the progress of the 

 disease (1893), and to our surprise, not one of them 



* On submitting specimens of diseased twigs and bark for examination 

 to the Entomological Section of the Museum of Natural History at South 

 Kensington, London our views were confirmed by the official report, 

 which was that the insect is " one of the Aphidce probably of the genus 

 chermes" (see also description of "The Larch Aphis" by Miss Eleanor 

 Omerod, consulting Entomologist R.A.S., in her Manual of Injurious 

 Insects, 2nd Edit. 1890, pp. 222 to 226). 



