The Mm and its Insect Enemies. 193 



differ as much from healthy trees of the same species as in their 

 general decrepitude of stem and branch. 



But suppose we should for the moment grant that these 

 insects sow the first seeds of dissolution in the life of the tree, 

 will the procede Robert recover them? In attempting an 

 answer to this question we might discourse at considerable 

 length on vegetable physiology, but there is no occasion, for the 

 simple reason that we could say nothing new. M. Robert is 

 said to strip the trees of their bark entirely, " the scolytus and 

 cossuses are instantaneously annihilated, the trees throw out 

 new layers of liber and even increase in bulk more rapidly than 

 their mutilated contemporaries." — (Times, January 30, 1862.) 

 If this is a correct account of the process, M. Robert is bold 

 enough to strip the trees down to the cambium layer, which 

 would no doubt clear away scolytes, leave cossuses untouched, 

 and cause the death of the trees the same season. But we are 

 very much of opinion that M. Robert has been misrepresented. 

 In two letters addressed to us on the subject by M. Robert, he 

 repudiates the idea of stripping a tree of its whole thickness of 

 bark, and admits that such an operation must be followed by 

 speedy death. He says, moreover, that he proceeds cautiously 

 in removing vermin from the outer bark, and at the same time 

 endeavours to renew the roots of the affected trees in order to 

 promote a free flow of sap and a more active vegetation. More 

 than this, M. Robert denies that he has had anything to do 

 with those wretched elms that are to be seen in some of the 

 avenues of Paris, tied with haybands, splintered up with 

 barrel staves, and variously sliced and chopped about as if 

 elaborately operated upon by means of a knife and fork.* 



We may come now to a more reasonable view of the case. 

 M. Robert is said to have recovered thousands of trees. But 

 this has not been done by " flaying" them. He removes the 

 outer layers of corky bark, which are often wholly occupied 

 with colonies of insects. The removal of these may be of no 

 immediate benefit to the tree, but the scraping away of the 

 rough external bark without hurting the liber, to say nothing of 

 penetrating to the cambium layer, has the effect of quickening 

 the flow of the sap and improving the health of the tree, and 



* " Les principales objections qui sontfaites a, mon systeme de traitement des 

 arbres (scarified elm-trees), reposent sur une fausse interpretation. II est Evident, 

 que si j'enlevais l'ecorce d'un arbre dans toute son epaisseur, ou jusqu'au bois, dans 

 l'esperance de le sauver, je justifierais la comparaison : 'An operation not much 

 less bold in its own way than that of flaying a human being.' Le rernede seroit, a 

 coup sur, pire que le mal. Mais ce n'est pas ainsi que je procede : je laisse, par 

 un procede quim'est propre, assez de tissu cortical pour prevenir l'accident qu'on 

 semble redouter, tout en detruisant avec certitude les larves ou vers qui toute 

 l'ecorce renferme, et cela, progressivement, pendant la guerison de l'arbre." — 

 Extract from a letter from M. Robert to the writer of this paper. 



