488 



widely distributed tip blight, appearing suddenly in many individuals, must 

 be the result of electricity. The most important point to which the author 

 himself calls attention is that lightning usually strikes below the top, injuring 

 the trunk, but leaving the crown uninjured; in other observed cases whole 

 trees have died, but never the crown alone. In discussing the objections of 

 other pathologists who consider that this blight is due to beetles or leaf 

 rolling caterpillars {Grapholitha pactolana)^, v. Tubeuf emphasizes the fact 

 that the the trees show the characteristic symptoms of disease when the 

 bark beetles are absent, and that these, attracted by the smell of turpentine, 

 appear only secondarily. Some pines and larches behaved like the spruces. 

 In spruces injured by lightning, the dead wood is found in the form of brown 

 strips of bark, surrounded by cork, lying within the otherwise green and 

 fresh bark, and below the dead tops. v. Tubeuf could not find this either 

 in trees which had been broken ofif, bent or eaten off, nor in others which 

 had been frozen or killed by insects. 



Further investigations'- proved that the anatomical characteristics of top 

 blighted spruces, are identical with those found in trees where lightning had 

 produced extensive injuries. The main support of the theory, however, lies 

 in the fact that v. Tubeuf and Zehnler"', by means of experimentally pro- 

 duced sparks, were in a position to produce, on the living trunk, external 

 appearances of top-blight as well as all the similar anatomical pathological 

 phenomena, viz., the dead "bark-eyes" which are surrounded by a layer of 

 white cork. So long, therefore, as it cannot be proved that other causes 

 produce the same symptoms, we must hold to the fact that the kind of top 

 blight described is a result of electrical discharges. These, in themselves, 

 may be weak, but v. Tubeuf states that in his experiments with deciduous 

 trees, and in his observations in the field, electrical injuries do not radiate 

 far into the healthy tissue. In artificial electrical injur)-, the leaves died 

 only to a certain point. 



In order to facilitate the conception of electrical discharge, v. Tubeuf 

 calls attention to the St. Elmo's fire'* and has produced this experimentally. 

 He refers in this to earlier experiments by Molisch"'. Inspired by the ob- 

 servations which Linnaeus' daughter and son had made on the effect of 

 lightning on flowers, he produced a light cluster, i. e., a shiny but quiet 

 electrical equalization. 



In V. Tubeuf 's experiments, potted plants were insulated by being 

 placed on a ball of wax. The soil was connected by a copper wire with one 

 conductor of an induction machine and a wire was likewise fastened to the 

 ball of the other conductor. As soon as the machine was set in motion the 



1 See MoUer in Zeitschr. f. Forst- u. Jagdwesen. 1904, Part 8. 



- V. Tubeuf, t)ber den anatomisch-pntholog-ischen Befund bei gipfeldiirren 

 Nadelholzern. Naturwiss. Z. f. Land- u. Forstwirtsch. 1903, No. 9, 10, 11. 



3 V. Tubeuf u. Zehnder, tJber die pathologrische Wirkung- kiin.stlich erzeugter 

 elektriseher Funkenstrome auf Leben u. Gesundheit der Nadelholzer. Sonder- 

 abdruck. 



•1 V. Tubeuf, Elmsfeuer-Versuche. Naturwi.ss. Z. f. I^and- u. Forstwirtsch. 

 1905, Part 5. 



5 Molisch, Leuchtonde Pflanzen. Jena 1904, G. Fischer. 



