420 GENERAL OBSERVATIONS. 



BEETLE, THE PYKALIS, THE PEOCRIS AMERICANA, THE HALTICA CHALT- 

 BEA, THE LEAF HOPPER, THE BOMBTX QUATA, THE PHILAMPELUS, 

 THE CHOEROCAMEPA, THE RHYNCHITIS, FUNGI, COMMON MILDEAV, ERY- 



SIPIIE, BOTRYTIS ; OF THE FKUIT AND FLOWER THE ROSE-BCG, 



SHANKING. 



§1. — GENERAL OBSERVATIONS. 



The diseases of plants have never received the 

 attention which they deserve. Of latter years in- 

 vestigation has been directed to insects injurious to 

 vegetation ; but this has been done more in relation 

 to entomology than to pathology. We had de- 

 scribed a great number of diseases affecting fruit 

 trees, and had classified them in such a manner as 

 we had hoped might contribute to the progress of 

 vegetable pathology, wdien we discovered that its 

 introduction to this volume would increase its size 

 beyond proper proportion. Therefore we are con- 

 strained to retain many of the results of our inves- 

 tigation on this topic, which we may hereafter issue 

 in a separate form. In this chapter we insert only 

 some leading facts on the more common diseases. 

 Even these we must treat with special regard to 

 practice, omitting, for the most part, those novelties 

 and freaks of nature which should be noticed in a 

 full pathological treatise. 



We shall not confine ourselves to a strictly philo- 

 sophical method ; because, in the cultivation of some 

 plants, the very state which we desire to induce is 

 one of disease, provided this be considered as a de- 

 parture from the normal type. For instance, the 



