A branch is seen emerging on the right, forming a “pin,” which would be obnoxious to bowyers. ] The conditions just described were artificial and abnormal, but varying temperatures, if extreme, might act in a similar manner. Sequoias and red-woods may naturally form several concentric wood rings in a year, a result probably due to alternations of heat and cold. Against the danger of over-calculation of age from neglecting such factors, may be set the consideration that, owing to damage by frost, or to seasonal peculiarities, no ring may be formed within the year[955]. In normal circumstances, “one ring, one year” is a trustworthy maxim. Unfortunately, to verify this rule, should its accuracy be challenged, the tree must be cut down--a most undesirable proceeding. Moreover, if the tree be aged, counting the rings is a matter of some difficulty; one must use a lens and a pair of needles, moving these “counters” as if scoring at a game of cribbage. Now Dr Lowe, while doubting whether the yew may not form more than one ring per year--a contingency that would seriously upset all computations based on this system--feels confident that in this country young trees produce one only. He is of opinion that the ring test consequently holds good for uninjured trees up to 200 or 250 years. Beyond that period, he asserts confidently that the yew sustains injuries from storm or disease sufficient to invalidate the rule. To the extent, let us say, of 250 years, Dr Lowe’s assumption runs parallel with that of De Candolle, who believed that there is practically no limit to the age of the yew, except disease. After the third century, Dr Lowe, as we shall soon see, actually claims a more rapid rate of growth, at least, intermittently. The errors to which De Candolle’s method is liable are thus epitomized. A yew which has been maltreated by lopping or injured by the browsing of animals may thicken and form bosses, and so increase the apparent girth. Trunks may be fused together. Wounds may prevent the formation of rings. Small shoots may be enveloped by the spread of the “bark,” and thus a vast number of rings may be formed which eventually become concentric[956]. Nevertheless, since we cannot always cut a tree down, some other method of estimating the age must be followed. And if the actual circumference be not always the true measure of the normal free-growing parent stem, our observations should, by way of counterpoise, be correspondingly numerous. Whoever has attempted to measure a yew, with the object of employing De Candolle’s rule, will recognize the force of Dr Lowe’s contentions, yet one cannot but think that the risk of error has been exaggerated.