Young, healthy, vigorous growing trees, that have become damaged or diseased, should in the majority of instances be attended to; but in the case of old specimens on which a great amount of labour and money would necessarily have to be expended, several important bearings must be considered before works of repair are taken in hand. Historic and valuable trees, those occupying prominent positions on a lawn or park, town trees where vegetation is scarce, and such as are not too old and fragile, may be dealt with within certain bounds, but to doctor all diseased and hollow trees on the most approved principle in such places as Epping Forest or Burnham Beeches would be highly imprudent, whether in view of the little benefit which in many instances would accrue by so doing or of the great expense involved in such an operation. The filling, too, must be adapted to circumstances, and to deal with the entire trunk of a hollow tree is in most cases quite out of the question, both from the point of utility and expense. Short-lived trees, such as the Alder, Birch and Poplar, or such as are liable to sudden attacks of insect and fungoid pests, and those that are unfavourably situated in mining and chemical areas, should be scantily dealt with, but the practical woodman will see at a glance which trees are best worthy of his attention and treatment. Probably the simplest, and certainly the cheapest method of dealing with diseased and hollow trunks is to clean out thoroughly all dead and decaying matter, the interior being scraped and swept with a rough brush, so that the loose rotting wood and bark is removed. When quite dry, the interior of the trunk should be painted with one, or preferably with two coats of creosote or carbolineum, and filled up with a composition of one part of Portland cement to three of clean gravel and sand, the surface coating at the orifice containing the largest quantity of cement. A coat of coal tar on top of the dry creosote goes far in making the concrete adhere firmly to the wood. When a fairly healthy tree is being operated upon, and when the bark is likely to grow over the exposed surface, the concrete should only be brought up on a level with the underside of the living bark; in other words, the cambium should be left free for expansion. Sometimes, brickbats, broken small, are used instead of gravel, but for various reasons concrete is preferable. The concrete surface may be prevented from cracking by applying annually a coat of paint, which, for appearance sake, may be of a similar colour to that of the bark of the tree.