Insects Injurious to the Elm. 35 



reproduction. A singular link between the forms of vegetable 

 and animal bone, if one may be permitted the use of such 

 fanciful terms, is to be found, in Crustacea?. The bone of the 

 lobster, for instance, unlike that of the higher forms of animal 

 life, is entirely external, that is to say, what would be the 

 internal spine, etc., in a fish or a quadruped is the shell of the 

 lobster. This external casing of bone is not only capable of 

 renewing itself in case of injury, but does so natural!}' every 

 year, the creature shedding its external bone to allow of the 

 annual growth of the body, which it clothes and protects. The 

 inner coating, analogous to the liber and alburnum of the tree, 

 having not only an inherent power of protection when deprived 

 for a time of their usual external covering, but having also the 

 power of re-clothing themselves with a new one of the same kind, 

 suited in dimension to the increased size of the body. So that 

 we need not be altogether surprised at the reported success of 

 M. Robert in doing- for the tree that which the lobster does 

 once a year for itself. It may be added that there is even a 

 " tree lobster/' as one may term it, which also does for itself 

 that which M. Robert pretends to do for diseased oaks or elms ; 

 that tree, is the well-kuown oriental plane, which sheds its old 

 bark every year, a circumstance which may partly account for 

 its retaining its health in the very heart of smoky towns, where 

 other trees perish, probably from the clogging of the pores of 

 the bark, and so stopping that necessary expiration which trees 

 cany on by them as well as the leaves. Just as in the human 

 being, the pores of the skin allow of a continuous expiratory 

 action supplemental to that of the lungs. The process of M. 

 Eobert, then, may possihhj, should it be found practicable, be 

 effectual, in permanently checking the ravages of the Scolytus 

 family; but it cannot touch the inroads of the Cossonus, and can- 

 not repair such damages as that effected by the larva of the 

 stag-beetle and the Cossus Ligniperda. 



I should add, in conclusion, that I have just received a 

 letter from a botanical physiologist who has entered into direct 

 correspondence with M. Robert, and who, after that corre- 

 spondence (as before) is decidedly of opinion that the 'procedc 

 Robert, as the French would say, is certain to be fatal to any 

 tree upon which it is fairly put to the test. A series of careful 

 experiments can alone decide the question ; and if judiciously 

 carried out, would, no doubt, lead to the elucidation of many 

 facts with which we are at present but imperfectly acquainted.* 



* The question raised in this paper is of great interest as a matter of vegetable 

 physiology ; but whatever may be the result of further experiments, we cannot en- 

 dorse the bone theory. — Ed. 



