THE NEW FORESTRY. 199 



and horses also browse on many kinds of trees, as may often 

 be seen in parks where the trees are usually cropped as high 

 as the cattle can reach. Cattle and sheep are not, however, 

 expected to be admitted into young plantations. 



SECTION III. INSECTS AND DISEASES. 



In the following list the species are taken in the order in 

 which they are given in Chapter VII., and those species that 

 do not suffer seriously from disease and insects are grouped 

 together. 



THE OAK. The foliage of the oak is often destroyed 

 about midsummer by the oak caterpillars Tortrix viridana 

 and Li par is monacha. Whole tracts are frequently quite 

 defoliated, not a tree escaping. The consequence is a 

 severe check to growth and a weak, ill-matured second growth 

 of leaves after the caterpillars have gone. Caterpillars are 

 always worst on poor, slow-growing trees, the growth of which 

 they quickly overtake.* They are always present in oak 

 woods to a greater or less extent, and are worse in some places 

 than others. The grubs also drop from the oaks upon the 

 underwood beneath, which they also defoliate, so that an 

 oak wood, badly attacked, presents a very miserable spectacle. 

 Drought and poverty in the soil seem to be the main predis- 

 posing causes. Flocks of rooks, starlings, and other birds 

 follow the caterpillars and destroy immense numbers, the 

 rooks gorging themselves to such an extent that they can 

 scarcely be made to rise. 



RING-SHAKE AND STAR-SHAKE. Whatever the cause of 

 this evil or disease may be, it affects the timber of the oak ori 

 many estates and destroys its value. In a ring-shaken tree 

 the annual rings of the trunk and main limbs are shaken 

 loose, so to speak, become detached from each other round 

 their whole circumference, hence the word " ring-shake." 

 There may be several shakes in the trunk, but there are 

 seldom two close together. Ring-shake ruptures the timber, 

 and when the tree is sawn up it falls to pieces and is worth- 

 less. A badly-shaken tree is said by timber merchants to 

 be " shaken like a besom," and where ring-shake is known to 

 exist to a serious extent the timber cannot be sold standing, 



* The geometer moth caterpillar, similar to the oak caterpillar, is also 

 invariably most destructive to pine plantations on poor, dry soils. (" Highland 

 Society's Transactions," 1897, p. JI 9-) 



