396 PLAIN AND PLEASANT TALK 



of temperature in the air and of moisture in the earth ; to 

 sudden change fromsward to high tillage ; and the result is 

 stated to be an " overphis " of sap, or a " surfeit." All 

 these causes occur every year; but the blight does not 

 every year follow them. Changes of temperature, and vio- 

 lent changes in the condition of the soil, may be allied with 

 the true cause. But when only these things exist, no blight 

 follows. 



4. Others have attributed the disease to over-stimulation 

 by high manuring, or constant tillage ; and it has been said 

 that covering the roots with stones and rubbish, or lay- 

 ing the orchard down to grass, Avould prevent the evil. 

 Facts warrant no such conclusions. Pear-trees in Gibson 

 County, Indiana, on a clay soil, with blue slaty subsoil, 

 were affected this year more severely than any of which 

 we have heard. Pears in southern parts of this State, on 

 red clay, where the ground had long been neglected, suf- 

 fered as much as along the rich bottom lands of the Wa- 

 bash about Yincennes. If there was any difference it was 

 in favor of the richest land. About Mooresville, Morgan 

 County, Indiana, pears have been generally affected, and 

 those in grass lands as much as those in open soils. Aside 

 from these facts, it is well known that pear-trees do not 

 blight in those seasons when they make the rankest growth 

 more than in others. They will thrive rampantly for years, 

 no evil arising from their luxuriance, and then suddenly 

 die of blight. 



5. It has been supposed by a few to be the effect of age^ 

 the disease beginning on old varieties, and propagated upon 

 new varieties by contagion. Were this the true cause, we 

 should expect it to be most frequently developed in those 

 pear regions where old varieties most abound. But this 

 disease seems to be so little known in England, that Lou. 

 don, in his elaborate Encyclopedia of Gardening^ does not 

 even mention it. Mr. Manning's statement will be given 

 further on, to the same purport. 



