INDIANA HORTICULTUitAL SOCIETY. 419 



then, the sap passes up from the roots, enters the leaf, and men are 

 astonished to see a branch, seemingly dead in the middle, growing thriftly 

 at its exti'emity. No insect theory can account for this case, yet, it is 

 perfectly plain when we consider that there are two currents of sap, one 

 of which may be destroyed and the other for a limited time go on. The 

 blight under this aspect is nothing but ringing or decortication, affected 

 by diseased sap destroying the parts in which it lodges, and then itself 

 drying up; the branch will grow, fruit will set, and frequently become 

 larger and finer flavored than usual. 



But in a second class of cases the downward current comes to a point 

 where the diseased sap had affected only a partial lodgment. The vital- 

 ity of the neighboring parts was preserved, and the diseased fluids have 

 been undried by wind or sun, and remain more or less inspissated. 



The descending current meets and takes up more or less of this dis- 

 eased matter, according to the particular condition of the sap. Wherever 

 'the elaborated sap passes, after touching the diseased region, it will carry 

 its poison along with it down the trunk by the lateral vessels, in toward 

 the pith. We may suppose that the violence which would destroy the 

 outer parts would, to some degree, rupture the inner sap vessels. By 

 this, or by some unknown way, the diseased sap is taken into the inner 

 upward current and goes into the general circulation. If it be in a 

 diluted state or in small quantities, languor and decline will be the result; 

 if in large quantities, and concentrated, the branch will die suddenly 

 and the odor of it will be that of frost bitten vegetation. All the different 

 degTees of mortality result from the quality and quantity of the diseased 

 sap which is taken into the circulation. In conclusion, then, where in 

 one class of cases the feculent matter was, in the faU, so virulent as to 

 destroy the parts where it lodged, and was then dried by exposure to 

 wind and sun, the branch above will live, even through the summer, and 

 perish the next winter, and the spring afterwards, standing bare among 

 gi-een branches, the cultivator may suppose the branch to have been 

 blighted that spring, although the cause of death was seated eighteen 

 months before. When, in the other class of cases, the diseased sap is 

 less virulent in the fall, but probably growing worse through the spring, 

 a worse blight ensues, and a more sudden mortality. 



I will mention some proofs of the truth of this explanation: 



}. The two great blight jears throughout this region, 1832 and 1844, 

 were preceded by a summer and fall such as I have described. In the 

 autumns of 1831-4.3 the orchards v^'ere overtaken by a sudden freeze while 

 in a fresh growing state, and in both cases the consequence was exces- 

 sive destruction the ensuing spring and summer. 



2. In consequence of this diagnosis, it has been found practical to 

 predict the blight six months before its development. The statement of 

 this fact on paper may seem a small measure of proof but it would weigh 

 much with any candid man- to be told by an experienced nurseryman 



