THE INFLUENCE OF MUTILATION ON THE FORM OF PLANTS. 515 



can be recognized years after by the flattened form of the crown, so diflerent 

 from the usual appearance, when the offending Birches have perhaps long dis- 

 appeared. Many other trees wage the same war with one another, the result 

 in each case being the mutilation and alteration of the form of the summit of 

 one of the trees. The Maple, for example, is either put quite hors de combat by 

 the long thorny branches of a neighbouring Gleditschia (Gleditschia triacanthos) 

 or else the crown becomes lop-sided owing to the destruction of the branches 

 on the side facing the Gleditschia. 



The way in which the appearance of Firs, Larches, Beeches, and Ling is 

 altered by the attacks of ruminants, especially goats, was described in vol. i. 

 p. 445, and we may add here that Pines and Junipers are mutilated in the same 

 manner. The consequence is that lateral branches, which would not otherwise 

 develop, grow out in the following year from the base of the twigs which have 

 been bitten off! Apparently no other alteration takes place in these plants. 

 But when huge boughs are broken oflF close to the ground by storms and the weight 

 of snow, when the tree-trunks of the forest are sacrificed to the wood-cutter's 

 hatchet, and the stems of seedling trees and shrubs in the meadow to the mower's 

 scythe, when all the young shoots are frozen by a night's frost in spring, or when 

 all the leaves are devoured by caterpillars and the branches are left bare as in 

 winter — then the consequences are much more serious. In these cases new shoots 

 make their appearance either from "' eyes " in the stem or from the reserve-buds 

 of the branches and twigs, or by buds produced by the roots below the ground. 

 The leaves of these shoots, or suckers, as they are called, diff'er very much from 

 those of the branches which have been broken, eaten, cut, or frozen off! The 

 leaves from the crown of the Aspen {Po2ndus tremula) are stiff" and smooth in 

 their adult condition; the circular blade is borne on a long petiole, and its margin 

 is coarsely notched and undulated. The lateral veins traversing the blade are 

 lost in a network near the edge in which no strong curved ribs occur. The leaves 

 of a sucker from the base of a mutilated stem, or from the root, are soft and 

 thickly covered on both sides with downy hairs; the heart-shaped blade is borne 

 on a short stalk, and the margin is beset with numerous upwardly-directed notched 

 teeth. The lateral veins of the blade merge near the edge of the leaf into a 

 network, in which strong curved ribs are plainly visible. The leaves from the 

 crown of the Oak {Quercus pedimciolata) ai-e deeply lobed and furnished with 

 two so-called auricles at the base; those of the suckers are quite entire or very 

 slightly lobed, with no auricles at the base. The leaves of the sucker of the 

 common Beech {Fagus sylvatica) are more or less plainly serrated at the edge, 

 while those of the topmost branches of the tree are quite entire. In the Black 

 Mulberry {Morvs nigra), and in the Paper Mulberry (Broussonetia papyrifera), 

 the leaves of the sucker have a sinuous margin and are more or less deeply lobed, 

 but those of the tree-top are heart-shaped with notched margins and no lobes. 

 The leaves of the sucker of the Birch {Betula verrucosa) are simply serrated, 

 with velvety hairs; those on the crown of the tree are doubly serrated and 



