No tree has such a remarkable faculty of covering up wounds or injuries by the growth of fresh wood from the outside; and even after the main stem is completely dead, fresh and entirely new stems may grow up around it and form a new tree around the dead one. For this reason most of the yews of very large size are mere shells, and even when no hollow can be seen from the outside, decay—which is often indicated by moisture running from holes in the trunk—has set in.
Three very curious sections showing the way in which these trunks grow are given by Lowe, pp. 78 and 79.
The yew, though occurring wild far north, as in Norway, is not perfectly hardy, and many instances are on record in which it has been injured or killed during severe winters. It was affected in Cambridgeshire[1] and severely injured at Glasgow by the severe frost of 1837–1838. In the winter of 1859–1860 the young shoots of many trees were killed at Burton-on-Trent.[2]
Many cultivated yews[3] were killed by the frost of 1879–1880 in Switzerland, Rhineland, Hessia, Thuringia, etc. though in the same localities other native conifers were not injured by the severe cold. Duhamel[4] states that in France the yew suffered much damage from the great frosts of 1709; and Malesherbes found several killed by the frost of 1789.
Poisonous Properties of the Yew
The poisonous properties of the yew have been well known from the earliest times, and the subject has been so carefully investigated in the Journal of the Royal Agricultural Society of England, 1892, p. 698, by Messrs. E.P. Squarey, Charles Whitehead, W. Carruthers, F.R.S., and Dr. Munro, and summarised by Low in chapter x. of his work, that we need not do more than give a brief résumé of the present state of our knowledge. Through the kindness of Sir W. Thiselton Dyer, we have been able to peruse a file of the Board of Agriculture entitled "Yew Poisoning," in which the subject has been further discussed by that gentleman with whose opinions we are in complete accordance.
The conclusions drawn by Dr. Munro, after careful study from a medical point of view, are as follows:—
"Both male and female yew leaves contain an alkaloid.
"This alkaloid in both cases appears to agree with the taxine of Hilger and Brande. Taxine is probably the poison of the yew, but it is doubtful whether it has ever been obtained in a pure state, and its physiological effects have not been sufficiently studied. Other alkaloids are probably present in yew.
"Taxine is present in fresh yew leaves as well as in those withered or air-dried. It is also present in the seeds, but not in the fleshy part of the fruit.
"The yew poison may be one of moderate virulence only, and may occur in greater percentage in male than in female trees, or the percentage may vary from tree to tree without distinction of sex, and this may explain the capricious
