things, that while the fungus grew vigorously up to a certain percentage of tannic acid, its development was very sensibly retarded if the percentage was slightly increased beyond this point. If the southern tree actually contains a large amount of tannin we should have here a fundamental barrier to the advance of the chestnut blight fungus, and thus a decided advantage in favor of the southern representatives of the species. However, as I have already intimated, the whole matter is theoretical, since there is entirely insufficient evidence to substantiate it.
If we summarize, then, the points which the American chestnut has to its credit on the asset side of the balance sheet, we find that it exhibits a rapid and vigorous growth, it is fairly tolerant, at least in youth, it is not over particular as regards soil requirements, it enjoys longevity as an inherent characteristic, it reproduces itself by sprouting from the stump, and finally, as regards the trees in the southern section of its range, their supposedly larger content of tannin may prove to be a protective power against the annihilating advances of the bark disease.
This list is impressive—in fact, one could hardly conceive how the species could be more favored, and, indeed, these are undoubtedly the main reasons why it has been so firmly established and abundant throughout its range.
When we review the troubles by which it is assailed on every hand, it is remarkable how many of them are due primarily to man's activities: as, for example, the introduction of the bark disease, continued forest fires, repeated coppicing, change of soil conditions from cutting over large areas, etc. And although through the efforts of a few some of the evils may be checked or diminished, from the complex nature of the case, the deadly work will inevitably continue. One can not avoid the conviction, therefore, that, if the present conditions persist, the virtual extinction of the American chestnut is only a question of time. In the south it is dying out where it once flourished, and in the north its general condition is such that it may soon cease to be classed as an important timber tree. How long it will survive it is of course impossible to predict with any degree of exactness. But at the present rate of decline its future life may possibly be measured in hundreds of years, but not in thousands.
The most hopeful indications for chestnut in North America in the future lie along the line of breeding experiments. Since the blight is our worst enemy, work on the development of varieties immune to this is of the highest value. It has long been known that certain Japanese forms are somewhat resistant to the blight, and the disease is comparatively inconspicuous on the Chinese chestnut, on which it has recently been found.[1] Fortunately work on hybridization of chestnut species had been started long before the blight was discovered in this country. Among
- ↑ Metcalf, Haven, loc. cit.
