_Shot-holes_ are perforations in leaves presenting the appearance, from their more or less rounded shape, of gunshot wounds. They may be due to insects which bore through the young leaves while still folded in the bud--_e.g._ Willow Beetle--or which gnaw out the tissue--_e.g._ the Beech Miner. Similar but usually more torn and irregular holes are eaten out by many caterpillars--_e.g._ the Cabbage Moth. Shot-holes on Peas may be the work of Thrips. Leaf perforations are commonly caused by severe hail-storms, the hail-stones beating right through the thin mesophyll. Certain chemicals used for spraying have also been known to cause shot-holes by killing the tissue beneath the standing drops. There is, however, a class of shot-holes in thin leaves which are due to the action of minute fungi, the mycelium of which so rots the tissues in a more or less circular area round the point of infection, that, in wet weather, the decomposing mass falls out and leaves a round hole--_e.g._ certain Chytridiaceae, Peronosporeae, _Gloeosporium_, _Exoascus_, etc. If dry weather supervenes these holes frequently dry at the edges, and the leaves appear as if eaten out. Shot-holes in Cherry, Walnut, Tobacco, and Plum leaves are due to _Phyllosticta_, in Cherry leaves also to _Clasterosporium_, and in Potato leaves to _Haltica_. _Frost-cracks._--The trunks of trees exposed to the north-east, and occasionally with other aspects, are apt to show longitudinal ridges which realise on a larger scale the features of healed wounds scored with a knife. These wounds are due to the outer layers of wood losing water from their cell-walls as it congeals to ice in their lumina, more rapidly than do the warmer internal parts of the trunk; as this drying of the wood causes its shrinkage, especially in the tangential direction, the effect of a sudden frost and north-east wind is to rend the wood, which splits longitudinally with a loud report, as may often be heard in severe winters. Since the cortex and bark are ruptured at the same time the total effect resembles that of a deep knife-cut, and the same healing processes result on a larger scale when the wood swells and closes up the wound again in spring. But this recently-closed lesion is evidently a plane of weakness, and if a similarly severe winter follows the wound reopens and again heals, and so on, until after a succession of years a prominent _Frost-ridge_ results, which may finally heal completely if milder winters ensue or the tree be eventually protected.