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Page:Popular Science Monthly Volume 24.djvu/271

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CONCENTRIC RINGS OF TREES.

CONCENTRIC RINGS OF TREES.
By A. L. CHILD, M.D.

IN the December number (1882) of the "Monthly," you published an article prepared by me, on the "Annual Growth of Trees," which has been somewhat largely commented upon, in the periodicals and press of the day, as also by the "American Congress of Forestry" at St. Paul. I am glad to note this interest in the subject, as it will cause more accurate observation of the facts in the case. As many of my critics have apparently read only extracts from the article, and have accordingly drawn very incorrect inferences as to my views, I wish to restate some of the more important points, and the evidence sustaining them.

In June of 1871 I planted a quantity of seed as it ripened and fell from some red-maple trees. In 1873 I transplanted some of the trees from these seeds, placing them on my city lots in Plattsmouth, Nebraska. In August, 1882, finding them too much crowded, I cut some out, and, the concentric rings being very plain and distinct, I counted them. From the day of planting the seed to the day of cutting the trees was two months over eleven years.

On one, more distinctly marked (although there was but little difference between them), I counted on one side of the heart forty rings. Other sides were not so distinct; but in no part were there fewer than thirty-five. There was no guess-work about the age of this tree. A daily record of meteorological events for the Smithsonian Institution and Signal-Office for over twenty years, and a life-long habit of daily record of all important events, had led to much care and caution in such matters. Hence, from my own record, I knew the tree had but twelve years of growth; and yet, as counted by myself and many others, it had forty clear concentric rings.

Here permit me to quote a few lines from the original article, which, so far as I have seen, have been entirely ignored or overlooked by all commentators: "I could select twelve more distinct ones (rings) between which fainter and narrower, or sub-rings, appeared. Nine of these apparently annual rings on one section were peculiarly distinct; much more than the sub-rings. But, of the remaining, it was difficult to decide which were annual and which were not." When first cut, and while the wood was green and the cells filled with sap, these rings were very clear and plain; but, as the water evaporated and the wood contracted, they showed less plainly. I have a section of it now before me, and I can not make out clearly over twenty-four, where, when green, forty were clearly visible. This section was not at first so distinctly marked as a section forwarded to Professor Cleveland