A far graver indictment of De Candolle’s figures is contained in the insinuation that his selected trees were stunted and ill-grown, so that the rate of growth was made to appear too slow[959]. The supposition, if well grounded, would severely shake De Candolle’s rule, but at present it is a supposition merely, as readers of the _Physiologie Végétale_ may learn for themselves. De Candolle did indeed believe that trees die from accident or disease rather than from old age, but how could the bias resulting from such an opinion make the age of a yew greater than it actually was? An injured tree whose development had been arrested would be credited with too few years rather than with too many. Take the case of the Tandridge yew, in Surrey (Fig. 71). Aubrey found that this tree had a girth of 30 feet at a height of five feet from the ground. Manning and Bray, about 130 years later, gave the corresponding measurement as 32 feet 9 inches. To-day the reading is only 32 feet 4 inches. Allowing for some discrepancies in the modes of measurement, the results are striking. The explanation is that, though the tree is still vigorous, it has long been hollow, and growth must have been slight, if indeed there has not been an actual arrest for the past century. The method, adopted by the two Christisons, of measuring a tree at known intervals of time, is perhaps open to less objection than that of assuming a mean rate of growth, based on the enumeration of the rings of selected specimens. A combination of both systems would be better, if not ideal. The “interval method,” nevertheless, overlooks the objection that growth is not quite uniform. De Candolle urged, as already noticed, that the rate diminishes in aged trees, and gave several reasons. The roots are farther from the air, and they are also working in competition with those of neighbouring trees. Should the soil be rocky or otherwise uncongenial the lessened elasticity of the bark retards growth. Add to these factors the likelihood of oncoming disease, and the slackened development would be appreciable. Against these considerations, Dr Lowe boldly affirms that “there is abundant evidence to show that old trees grow, at intervals, much more rapidly than young ones”; but he makes this concession: “they do not, as I have said, grow uniformly, but have periods of comparative arrest of growth[960].” These pauses, he believes, are due to the overshadowing head of the tree. Were the head to be broken every half century or so, rapid growth would again commence. But to what degree does such a pollarding occur in nature? Does not the head continue, in the main, to overshadow the trunk and roots? (The lopping of yews for making bows, as apart from true pollarding, will be discussed later.) One reiterates, all systems are liable to error, but some systems are more accurate than others. And the “interval method,” especially if supplemented by estimating the total