DR. ZIMMERMAN: I don't think so. They are doing it with other things. I found a human being giving the reaction for typhoid for seventeen years after he had been immunized. DR. SMITH: Have you any evidence for or against the decline of immunity in the tree? DR. ZIMMERMAN: I think it will decline. DR. SMITH: Then we have got to keep on immunizing like spraying. I didn't mean necessarily annually. I mean perhaps it is not a permanent achievement. DR. ZIMMERMAN: I imagine that the tree will be sufficiently attacked by blight to keep the immunity up. It is wise to have it attacked once in a while. MR. HERSHEY: Isn't this only carried on until you get natural resistance? DR. ZIMMERMAN: I know that it will be a long time before I can have chestnut trees to produce like Mr. Harrington's. But I am going ahead. I can't wait 17 years. All I need is some time and I will produce chestnuts of the finest varieties, as Mr. Harrington has. DR. SMITH: How long will it take? DR. ZIMMERMAN: They will hold their immunity as well as the Chinese. The ones I have are worth planting right now. I have trees that are standing up better than any Chinese chestnuts are. It takes a long time before the immunizing principle is so disseminated that every part of the tree will have an equal resistance. I can easily see that by cutting off a scion and grafting it I may get hold of one that has not had its immunization distributed as it should be. DR. SMITH: A fairly ignorant man can take machinery and spray an orchard. Can he do the same with immunizing? DR. ZIMMERMAN: No sir, he can not. DR. SMITH: Perhaps I should not have used the word ignorant. A farm hand can spray and make a pretty good crop of apples. DR. ZIMMERMAN: No, he can't do it. It hasn't been easy. I have run into all kinds of obstacles. As soon as I injure the stock a little bit the blight takes it. As soon as I can raise them on their own roots it will be all right. That will come. DR. SMITH: Have you seen chestnut grafts root as the apple does? DR. ZIMMERMAN: Yes, right below the surface. A couple of them were that long. They will send out roots. Then I have noticed on some, that at the place where I grafted the callus got quite large. It got too dry and died off. I have never rooted American chestnut cuttings. I have rooted some Chinese chestnuts. THE PRESIDENT: Some of the Chinese chestnuts root quite readily from those small shoots that come up from the ground. I conducted a little experiment in trying to propagate the Chinese chestnuts by cuttings. I made 144 cuttings. They all dutifully and beautifully died. I don't mean to say that the Chinese chestnut cannot be rooted by cuttings.