482 



circular places on the surface from which the bark had been removed. 

 These places seem to be produced as a result of the very great local drying 

 of young wood and were colored by concentric, dark yellow and brown 



^L^:^^^^ 



Fig:. 97. An oak 23 m. high, which lias been struck by lightning. (After Nobbe.) 



clri.Ml'T,Te\'''''^!i'f,,'',''''''''^ •"■:""''' 'M"l.Joi"txl the trunk, b. <■, rf bra,>cl,es i„juml at tl,eir h.-,sc winch have 



UntH I.itei.. hranch reniaimi.sr uninjured,// ami /// hanginR pieces of wood, r and i s,„all br.-.nches 



injured in the sapwootl. 



rings. A number of other causes have also become known, in which small. 

 circular spots indicate the entrance or exit of the flash of lightning. 



R. Hartig, in his text book^ gives especially clear illustrations of the 



different k inds of injury due to lightning. He traces the difference in the 



1 Hartig, R., Lehrbuch d. Pflunzenkrankheiten. 3d Edition, 1900. Berlin, J. Springer. 



