Professor Bonney — Plant-stems in Gneiss. 219 



quartz veins and exhibits (as illustrated bj^ a photograph) irregular 

 folds, the crests of which are roughly parallel with the supposed 

 stem, besides other mechanical disturbance. The result of the 

 investigation, into the more minute details of which it is needless 

 to enter, is summed up in the following words: "Der vermeintliche 

 Stamm erscheint als ein Amphibolit-Einschluss, der beim Faltungs- 

 process gewalzt worden ist " : in other words it is not a fossil plant, 

 but a lusus naturcc. 



The authors, however, leave without notice some interesting 

 questions. We should welcome some explanation of these isolated 

 and singularly shaped portions of hornblendic rock in a mass which 

 elsewhere is generally without that mineral. Are we to i-egard 

 them as branches of an intrusive vein of dioritic rock, rolled round 

 and perhaps broken up by mechanical movements; or were they 

 originall}' concretions, somewhat similarly affected, and if so, iiow 

 are they to be explained ? These questions the authors dismiss with 

 the brief remark that such hornblendic inclusions are common in 

 the Guttannen gneiss. That may be so, but I cannot remember 

 to have observed another instance, and in the rock itself hornblende 

 is seldom, if ever, present. In no one of twenty-four slices in my 

 cabinet, three of them, according to report, from the same block 

 as the specimen at Berne, can I find an indubitable grain of 

 hornblende. Again, what explanation must we give of the biotite 

 ' skin,' which so curiously miniics a ' bark.' Was it a contact 

 product of the gneiss and tlie amphibolite, or a secondary result 

 of their juxtaposition and of mechanical disturbances? Yet more, 

 how do we account for the curious petrographical character of the 

 so-called Carboniferous gneiss, which is so distinctive as to catch 

 the eye at once in the fiehl, and to have led the official geologists 

 of Switzerland to distinguish it from the other gneisses of the 

 region?' I am fairly well acquainted with Alpine gneisses, and this 

 one, so far as I can remember, differs from all others known to me. 

 The ' mortelstructur ' also, exhibited by certain specimens from 

 Guttannen, appears to me abnormal. From the majority, which 

 neither resemble true gneisses nor those called mylonitic, it is 

 absent ; in the few, where it occurs, the presence of a fragment 

 seems possible. 



But I must admit that, though some aspects of the problem seem to 

 have been overlooked by the authors, their petrographical description 

 of this Guttannen gneiss makes it impossible that these structures 

 can be the remains of plants. Hence, whatever the rock may be, 

 they cease to have any special interest. They do not reveal its 

 geological age, and the inferences founded on them are fallacious. 

 That a mistake had been made, I was confident from the first ; but 

 of the two possible explanations of it I have apparently adopted the 

 wrong one. Though I naturally regi-et this, I cannot but rejoice 

 at the effectual laying of another metamorphic spectre, and for that 

 we are deeply indebted to Messrs. Von Fellenberg and Schmidt. 



' Near Guttannen they term it Seiitisclie riiyllite, an inappropriate name, a* 

 I understand Phyllite. 



