STATE HORTICULTURAL SOCIETY. lOl 



living bark of trees, under favorable conditions they quickly grow, and each becomes 

 the center of a new cluster of cells; these, as they grow, force their way into the 

 living tissues which they reduce to an unhealthy condition, gradually penetrating into 

 it until they reach the alburnum or newly forming sapwood. "When these unicellular 

 plants are once in contact with the albunuim or newly forming sapwood, and the con- 

 ditions for their growth are most favorable, they increase with astonishing rapidity. 

 So rapidly may they increase, that in a single night, or two at most, they vrill disperse 

 themselves through a square inch or more of space. As this growth goes on the little 

 cells push into the newly forming cellular parts of the tree, and as' far as they penetrate 

 they separate the little wood cells of recent formation, thus breaking up the organ- 

 ized channel of circulation, and feed on the juices which are liberated, and flow into 

 these wounded parts . 



If the circulation in the trees is very active, so much sap is diverted into these 

 wounded places and thence out through the spongy or wounded bark, as to run down 

 many feet on the branches or trunks of the trees. Could these little fungoid plants or 

 cells which we have described always remain as we at first find them , then the harm 

 they could inflict on trees would be so trifling, as compared with the injury they 

 really do, as scarcely to deserve a passing remark. 



All individual living organisms, however, be they animal or vegetable, after per- 

 forming their functions, die, giving place to others of their kind. So it is with the 

 little one-celled plants of which we are treating. These run their course in a few 

 hours or days, when the substance of which they are composed breaks down, and 

 their sappy or watery parts mix with the sap or juices of the tree. This mixing the 

 juices of the one-celled plants with the sap of the tree, probably, dissolves the little 

 particles of which the sap in the trees is made, much in the same way that certain 

 substances, when introduced into the veins of men or animals, are known to break 

 down and dissolve the little flattened globules of which the blood is composed. 



When the blood of man or animals becomes deranged by mixing with it substances 

 that will dissolve it, as by the introduction of milk into the veins, or injection of 

 poison by the bite of reptiles, then ulceration of the parts, or death of the animal is 

 the invariable result. Nor do we find the mixing of the juices of the one-celled 

 plants, of which we have spoken, with those of trees, less fatal to trees, than is the 

 vitiated blood to animals. ■ 



In my report to the Illinois Horticultural Society for 1868, 1 detailed my experiments 

 in inoculating healthy pear and apple trees with blight. To that report I will now 

 add that pear, apple and quince tree blight appear to be identical, since the little 

 cellular growth when taken from one of these trees and introduced into the circula- 

 tion of either of the others, it will induce the disease, to all appearance, the same as 

 when it occurs in the usual way. It is by the process of inoculation that I was able 

 to determine that the little cell growth of which I have spoken, was the cause of blight. 



By collecting on a camels' hair pencil a number of the little cells found on the bark 

 which was enclosed in the bottles, as I have before described, and put them in contact 

 with the newly forming sap-wood of healthy trees, then the disease will appear in the 

 inoculated part in from two, four or six days, varying in the time, according to the 

 state of the weather. 



In the early part of the season of the tree's growth, it generally requires about four 

 weeks for the little parasitic plants, which are the cause of blight, to pass through the 



