( iöi ) 



stuck <o the radiclos, (o ho sure, hul oiilv lo old, dyinu-, nol Jo 

 fresh and growing roots. 



Wigand gave no explanation. To liin» ii seemed to he "ein bis 

 jetzt nngelöstes nieehaniselies Paradoxon, nielit minderals Mimcldiausen, 

 der sieh nnd sein Pterd an seinein eigenen Zopfe ans deni Snni[)te 

 zielit" '). 



Bnt he entirely eonf'nsed the force witii which the root penetrated 

 and the cause which })revents the seedling from capsizing iji the 

 mercury. For he thought the penetration of gernu'oots in a solid 

 soil quite as mysterious, although here there was no (piestion of 

 upward pressure. 



No attention has later been paid to these observations; not even 

 by those who quoted various other points from this chapter of Wigand. 

 It was considered sufficient to refer to the refutation by Dikam) 

 and DuTROCHET in 1845. 



So HoFMEisTF.R wrote in 1860'-'): "Pinot nnd Payer sind bercits 

 1845 durch Durand und Dutrochet so griindlich widerlegt, die 

 Ursachen der Tauschungen jejier sind so Aollstandig aufgedeckt worden, 

 dass die ausführliche Mittheilung ^on mir selbst über diesen Gegen- 

 stand angestellter Beobachtungen kaum noch nöihig ist" ■). HoF:\rEisTKR 

 obtained the same result as Durand and DiTuoruET : })enetration 

 by Aveiglit or because the seedling stuck to llie niei'cui'y by (h'ssolxed 

 matter. 



Sachs wrote in 1865: "Die an sich schon unglaublich klingenden 

 Angaben Pixot's und Payp;r's über das tiefe Eiiulriugen der Wurzelii 

 in Quecksilber, wurden schon von Dl'rand und Dutrochet widerlegt" "). 



In 1867 Hof3!EISter wrote tliat the penetration of growing roots 

 into mercury was caused by stretching of the hypocotyl, "\\ie 

 bereits Durand und Dutrochet erschöpfend gezeigt haben" ''). 



Experiments on germination upon mercury no^v became very 

 fre({uent iii the follo\ving years iji order to combat IIofmeister's 

 theory of positive geotro})ism. This latter namely, like Knight's 

 theory, was based on the sujiposition thai the apex of the root was 

 of a plastic nature and therefore the penetration of the roots into 



1) 1. c. p. 140. 



~) W. HoFMiïiSTF.n, Uc])ci- (lie (liircli die Selnverkrafl boslinimicn Ricliliingcn 

 von Pflanzenlheilcn, in Berichte über die Verhandliingen der köii. Sachs. C!es. der 

 Wiss. zu Leipzig, Malliematiscli-Pliysisclie Classe, Xlltor Band ISGO. pag. 17.")— 2i:5. 

 The same article in PuixasuKiM's Jaliibiichcr fiii' wiss. Botanik III 18()3 pag. 77 — Hi. 



-) ]. c. p. 203 resp. p. 105. 



■^) J. Sachs. Ilandbucli der Experimental-Pliysiolngie dcr Pflanzon, 180"), pag. lOi. 



") W. HoFMEisTEu. Die Lelirc von der Pflanzenzelle, 1807, pa;/. 283 Anm. 4. 



