1847.] Blight in Apple and Pear Trees. 7 



destroyed. So, too, as in mortification of the limbs of animals, a 

 line of separation takes place between the dead and the living 

 parts, beyond which the disease does not extend. 



In accordance, then, with the above remarks, we have in many 

 instances of post mortem examinations, pronounced a verdict of 

 death from mortification; at the same time we have been con- 

 strained to add that in view of the primary cause we were in the 

 dark. 



There is nothing which conflicts, so far as we know, with the 

 view that all living structures may be subject to death from mor- 

 tification or gangrene. In animal structure gangrene results from 

 a variety of causes, and is always to be set down as an effect. In 

 aged persons the toes mortify, or the extreme parts which do not 

 seem to be duly supported by the fluids. In cases of high inflam- 

 mation the parts sometimes die or mortify, and are finally thrown 

 off if the part is not a vital one. It can hardly be supposed, how- 

 ever, that vegetables are liable to attacks of inflammation ; we may, 

 it is true, suppose that under a hot sun the fluids and the solids 

 may be acted upon in a manner analagous to that which results 

 in inflammation in animals — still we can by no means feel satisfied 

 that is truly the case. 



The gangrene or mortification which occurs in trees, seems of- 

 ten to result from want of vigor or strength in the tissues, though 

 by no means are we warranted in drawing the conclusion that it is 

 always so. When, however, we see a tree with rather delicate 

 leaves, and with long, straggling, pendant branches, losing its 

 leaves and branches in succession, we may suspect that there is a 

 want of ability to supply the amount of sap to preserve the vital 

 principle, and especially where we find that heading in the branches 

 results in stopping the progress of the decay, by giving more en- 

 ergy to the remaining parts. 



The death of vegetables from mortification described above, dif- 

 fers materially from death by the girding of the larvae of insects. 

 In this case there is not that peculiar unhealthy appearance of the 

 tissue of the parts beneath the cuticle, and generally the whole 

 limb dies at once down to the place where the insect has formed 

 its trench. The oak, and in truth many trees, are destroyed by 

 the operations of a girdler. This is a cause which is easily as- 

 certained, the whole effects of which resemble precisely the ope- 

 rations we often perform upon trees for the purpose of destroying 

 them; and we may add that the phenomena attending the death 

 of the tree or limb is precisely the same. The source of nutri- 

 triment in both cases is cut off", and the limb or tree dies simply 

 of starvation. There is in neither case an infused poison, but 

 merely a destruction in the continuity of the parts which transmit 

 the sap from the roots to the branches. In this case we are able 



