On January 11 the cambium ring at the lower end of the cuttings had begun to callus. On February 17 the upper bud on one of the cuttings began to push. Later some of the other cuttings began to swell preparatory to the development of new growth. All the cuttings, however, finally died. It appeared from their behavior that the temperatures to which they were subjected were too high for their best development.
In the other experiment the cuttings were placed in sand without sphagnum in a greenhouse at a temperature ordinarily of 50° to 65°, rising occasionally, however, on still, sunny days to 70°. After a few weeks, these cuttings were well callused and the buds began to swell slowly, exposing first their green bracts, and later on some of the cuttings the green compound leaves, pushing out from among the bracts. These cuttings also, however, finally turned black and died, but not until after the first of April.
The experiments showed that hickory cuttings, when taken at a suitable time of year and exposed to conditions suited to other hard wooded plants known to be difficult to root, retained their vitality and passed satisfactorily through the stages preliminary to rooting. While no actual roots were secured, the experiments suggest that the rooting of hickory cuttings is not beyond the possibility of attainment.
As the basis of an experiment this winter, I suggest that you select half a dozen twigs that you are willing to sacrifice on some good variety of hickory, and remove a ring of bark at a distance of 4 to 8 inches from the top. The ring of bark removed should be about half an inch in length and its upper end should come about a quarter of an inch below a bud. At the present season the bark will not peel from the wood. It will, therefore, be necessary to scrape it off, so as to leave nothing but the wood on the girdled area. The bark should be cleanly cut at each end of this area. I hope that we shall still have sufficient warm weather to induce the formation of a callus on the cambium at the upper end of this ring.
Later in the winter, some time in January, you can cut off these twigs and send them to me, packed as those were last year. The cutting is preferably made just below the ring. I would prefer that all the wood from the ring to the tip of the twig be of the past summer's growth. We can try, however, twigs containing two seasons' growth, if the others are not easily available."
President Morris: That is a suggestion, you see, of apparent value, because it has succeeded with blueberries,—this method of cutting off a ring of bark before the leaves are shed, allowing a ring to callous, then later cutting off this prepared twig and subjecting it to methods for striking roots. It is an extremely interesting suggestion. Just as soon as I heard of this procedure, I went out and prepared about fifty hickory and walnut twigs myself, but that was this autumn, and I haven't cut them yet for the experiments in rooting. Has anyone had experience along this line?
Mr. Collins: I saw an experiment in rooting, and I am prompted to ask if anything has been done along this particular line. The method employed was this. The twig was partially cut from the branch, perhaps cut three-quarters of the way through with a slanting cut. It was then bent a little, and a little sphagnum put in the cut, then a ball of sphagnum was wrapped about the whole cut area, and it was tied with twine, and that was kept wet for several months, I think, until, finally, new roots pushed through and appeared on the outside of this ball of sphagnum.
President Morris: I read of that. It was published in a government report.
Professor Collins: It was on the rubber plant.
President Morris: I tried it at that time on the hickory. The difficulty was in getting my men sufficiently interested to keep the sphagnum wet all the time. It promised something. The rubber plants, perhaps, would lend themselves more readily to such a procedure than the hickories, because most of the rubber plants are air plants, anyway. All of the Ficus family depend so little upon the ground for their nourishment.