382 STATE HORTICULTURAL SOCIETY. 



proved, except the one of fungus growth. In 1878 the writer announced to the 

 Illinois Horticultural Society the discovery of bacteria apparently connected 

 with the disease. His investigations were carried on in an orchard where there 

 were 94 apple trees, 20 pear trees, and one quince. "After finding myriads of 

 bacteria in the fluids of the diseased tissues," he said, " I inoculated several 

 pear and apple trees with what to me, at the time, were unsatisfactory but not 

 uninstructive results. Beginning on the first day of July, 1880, 1 experimented 

 in various ways at different times upon G6 trees of the pear, apple, and quince. 

 Of the numerous applications of the virus upon the unbroken bark or leaves, 

 none were successful. Of the inoculations there were successful 63 per cent of 

 the pear, 30 per cent of the apple, and 100 per cent of the quince. Upon the 

 pear and quince trees used for the experiments, the disease appeared only in a 

 single case except as the direct result of the inoculation. This latter was some- 

 times performed with a knife, sometimes with a needle, always with careful 

 precautions and close subsequent examination. Such experimental limbs as 

 permitted it were cut and preserved like herbarium specimens, and are exhib- 

 ited with the paper. 



The organism found answers fairly to the description of Pasteur's butyric 

 vibrion. They are usually oblong, rounded at the ends, mostly connected, two 

 together. Their motions are not rapid, consisting of turning in every direction, 

 and sliding irregularly forward. They are found within closed cells, in the 

 open spaces, and in immense numbers in the viscid exudations from the dis- 

 eased bark and leaves. The most conspicuous alteration observed in the tissues 

 is the disappearance of the starch grains from the cells. The cell walls are left 

 intact, and the protoplasmic portions remain until after the starch is mostly 

 absorbed, and appears to suffer little change until death ensues. The disease 

 is, par excellence, oue of the bark. The leaves die in consequence of this, or 

 are themselves invaded, either primarily or secondarily, by the destroyer. The 

 progress of the disease is always slow, but the leaves of an affected limb often 

 turn black quite suddenly, perhaps according to meteorologic conditions. In 

 diseased bark, before change has taken place visible from without, and while 

 the leaves are still green and fresh, an active fermentation occurs. This con- 

 tinues until desiccation or the exhaustion of the fermentable substances puts an 

 end to the process. The products of this fermentation are carbon dioxide and 

 butyric acid, or a closely similar substance. From the fact that virus from 

 the pear affects the apple tree, and vice versa, the speaker argued that the dis- 

 ease was similar in each. The experiments tended to show that the virus is 

 harmless upon the epidermis of healthy plants, nor does it penetrate through 

 the breathing pores. The speaker exhibited drawings of the cells of a healthy 

 plant and a diseased one, showing that the starch in the latter was gradually 

 absorbed. He obtained the virus from diseased trees, where it is exuded, and 

 placed it in distilled water. Upon the dead leaves and branches the virus dried 

 and looked like varnish. When re-dissolved it retains its vitality. The simple 

 puncture of a bark of a tree with a needle which had been dipped in the virus 

 would be sufficient to cause its death. Prof. Burrill exhibited a small vial 

 containing about a teaspoonful of the virus in solution, which he said was suffi- 

 cient to destroy a whole orchard. — Science. 



