Gilbert White thought that male trees are more robust in growth than female trees; but we are unaware of any accurate observations on this subject. Kirchner,[1] however, states that there is a slight distinction in the habit of the two sexes, male trees being taller with longer internodes and shorter leaves.
In early spring drops of mucilage may be observed glistening on the ovules of female trees in flower. The mucilage is secreted by the micropyle, and seems to entangle the grains of pollen which have been wafted on the ovules by the wind. The clouds of pollen which fly forth from the male flowers are well known. The pollen is liberated from the stamens by a very elaborate mechanism, which serves to protect the pollen grains in rainy weather. A good account of this is given by Kerner.[2]
A large quantity of fruit of the yew falls to the ground in autumn; but the seeds in this case do not as a rule germinate. Natural reproduction seems to be effected by birds like the thrush and blackbird, which, attracted by the fleshy aril, devour the whole fruit. The seeds, protected by their hard testa, escape digestion and are voided at a distance. They rarely germinate in the first year after ripening; seedlings come up as a rule in the year following, a few even appearing in the third year.
The buds of the different geographical forms appear to differ more than the leaves themselves. The terminal bud is invested closely by the uppermost and youngest leaves and continues the growth of the shoot. The bud scales on unfolding remain at the base of the growing shoot, and on older branchlets persist as dry brownish scales, forming an involucre at the bases of the branchlets. Lateral buds are developed on the twigs at irregular intervals. Many of these remain dormant, retaining the power to take on growth at any moment. This explains the readiness with which the yew submits to pruning, and the facility with which it produces coppice shoots when the stem is cut. Spray or epicormic branches are frequently produced on the upper side of the branches or on the stem; and these also originate in dormant buds.
True root-suckers are never formed; but layering occurs, though very rarely, in branches which have come in contact with the ground. (A.H.)
Age, Hardiness
With regard to the supposed great age of yew trees, which has been much exaggerated by authors—especially by the great Swiss botanist, De Candolle—we must refer our readers to Lowe, who has discussed the subject very thoroughly in chapter iii. of his work. He proves that the average rate of growth is about I foot of diameter in 60-70 years in both young and old trees. There is, however, abundant evidence to show that though old trees grow at intervals much more rapidly than young ones, they do not grow uniformly, but have periods of comparative rest, and that the increase of girth is fastest when old trees have lost their heads and the stem is covered with young shoots.
