While my work is still going on as an experiment I have no hesitancy in saying that I can and have put as much active immunity to the blight into the chestnut in five years as nature has been able to place in perhaps four or five thousand years by her usual method. However it is only fair to state that such results cannot be accomplished by mere oratory. Injections must be made and the antigen must go into the plants, not in single doses, if you please, but by the thousands.
In recent years there has been considerable discussion relative to the chestnut coming back. This simply means further delay. The chestnut will come back but not before from 25 to 150 years yet. There are few roots that will stand mutilation for that period, and the few plants that do survive will have taken the shrub form like the chinquapin, and the nuts will likely be as insignificant. I have plants from a tree that holds as much immunity in the natural way as any I know, being rated at 2X, and these plants have inherited an immunity equal to the parent, no more and no less. I have, however, a lot of seedlings from Paragon and Champion trees rated at from 6X to 7X. These seedlings may confidently be expected to perform as their parents and produce many plants of equal resistance.
I shall not discuss the antigen or its method of administration. That has been covered rather carefully in former papers. I do want to say a word, however, about root stock. In a blight region it is preferable to have chestnuts on their own roots. The nearest to own-rooted plants is a graft on their own seedlings. The Chinese and Japanese chestnut in my hands has made a very poor root stock for the American chestnut or its hybrids. The European chestnut is only fair, with the chinquapin somewhat better, but having the disadvantage of being troublesome to get from the seed. The American chestnut, or its American hybrids, is by far the best, providing we can get one with immunity. I think the Rochester will shortly fill this need.
The chestnut oak has made a rather interesting stock for a few varieties, notably a Chinese and 20 No. 3, a native American chestnut sent to me from Bloomsburg, Pa. I now have a few of these double grafted with other varieties.
I might say that I am no longer interested in any chestnut, no matter how resistant it may be, unless the nut is of large size and fine quality, because I can immunize a plant bearing a good size, fine quality chestnut much easier and in a shorter time than one can be developed through hybridization from an inferior nut. I am usually, like most folks, looking for the path of least resistance.
My work has been a good deal divided during the past few years because, while I started out with the chestnut alone, now I am carrying a dozen other fruits, nuts and berries.
In closing let me state that my principle of induced immunity is sound and the procedure feasible and practical.
The President: About the result of grafting the chestnut on a species of oak. How long have these scions been growing?
Dr. Zimmerman: About three years.