4^6 



This difference may be due to the fact that the disturbance from late frosts 

 occurs usually when the trees ha\e formed but little new wood, while the 

 injuries due to lightning are produced by summer storms later in the season, 



R. Hartig did not consider that the production of the collapsed strip of 

 tissue was the direct result of the action of lightning, for he says^ "if the 

 lightning takes its course, entirely or in part, in the young wood, it is seen 

 in this, that the cells remain unlignified and are pressed together by the 

 tissue structures produced later." He then gives statements, as does also 

 Beling-, on the death of whole groups of trees in which he found'' that the 

 bast was apparently killed in the pines struck by lightning and in numerous 

 adjacent trunks. The same observer also mentions a case in a mixed spruce 

 and oak forest, in which the spruces predominated, wherein only the repressed 

 (12) oaks showed traces of lightning, while the spruces were entirely unin- 

 jured. The fact that, in mixed tracts, the oaks suffer with especial fre- 

 quency from lightning has often been mentioned; just as also that other 

 trees, not distinguished possibly by their height and structure, in certain 

 localities fall victims especially to the lightning flashes*. 



In connection with the death of trees in whole groves, R. Hartig lays 

 emphasis on his observations that this advances radially in tracts of pine 

 trees, v. Tubeuf"' has recently studied this condition. He describes a case 

 in which only one larch apparently had been struck by lightning and yet a 

 considerable number of the surrounding pines and spruces began to die. 

 The larch showed an interrupted line of splitting extending down the trunk, 

 the top remaining green. The trees surrounding it showed no local injuries, 

 but died in a semi-circle of 25 m. Such cases have often been found. In 

 an earlier publication v. Tubeuf*' states the hypothesis that such dying 

 back of large groups of trees is caused by "Hghtning spray," i. e., by the 

 scattering of the lightning into a number of rays pencils ; while Ebermayer^ 

 traces the phenomenon to an internal lightning stroke, due to the sudden 

 union of electricities which had been separated. Through the influence of 

 the thunder cloud the opposed electricities divide in the tree ; the unlike, 

 negative, draws up to the upper part, while the other, positive, presses down 

 into the lower part. "Now as soon as the lightning strikes, the cause of the 

 separation of the two electricities inside a nearby body is removed and these 

 suddenly reunite in the same moment." v. Tubeuf cannot adopt this point 

 of view on the ground of the results of his artificial lightning experiments. 

 In the investigation of trees taken from lightning depressions, he found, 

 "coarse injuries due to lightning" in one or another trunk, and since other 



1 Hartig, R., I^ehrbuch der Prtanzenkrankheiten. 3d ed. 1900, p. 242. 



2 Zeitschr, f. Forst- u. Jagdwe.sen, Nov. 1873. 



3 Bot. Jahresbericht v. Just, 1875, p. 956. — Lehrbuch d. Baumkrankh. 1882, 

 p. 191. 



* Landwirt 1875, p. 400 u. 513. — Gard. Chronicle 1878, II, p. 667. 



■'■' V. Tubeuf, tJber sogenannte Blitzlocher im Walde. Naturwis.s. Z. f. Land- 

 u. Forstwirtsch. 1905, p. 493. (Bibliography here.) 



c Absterben ganzer Baumgruppen durch den Blitz. Naturwiss. Z. f. Land- 

 u. Fortswirtsch. 1905, p. 493. Bibliography here. 



■ Ebermayer, Wald und Blitzgefahr. Naturwiss. Rundschau. 1899. 



