1882.] 



on the ExcitahiUty of Plants. 



165 



it is certain thatthe electrical disturbance does not begin at the part 

 ^tS'if J^f !« interpolated between the galvanometer eleetrr^es 

 tT. nt • r #^, "^ "■ ^"""^ "^'"^ ^^^ ^^"tation. If, on extendinc. 



tlJ^U '^"'T- ^J^f " ^'>^^ ^^^ eff^et becomes ol^ 



servable, you are certain that the disturbance begins between three 

 and four hundredths of a second after excitation. 



By this method we have learnt, first, that even when the seat of 

 excitation is as near as possible to the lei-off spot, there is a 

 measurable delay and secondly, that its duration varies with Ae 

 distance which the excitation effect has to travel so as toTndidte 

 tha , in a warm stove, the rate of transmission is somethin.. like 2C^ 

 millimeters per second. It is, consequentlv. comparable ^tl the rate 



tl Zr"'"" """''"'"'' "'""'"'''' ■^^'"^^°- -^lie heL?o? 



And now I come to my last point, namely that the electrical 



change has always the same character under fhe same con^tfons! 



Fig. 10. 



Copy of photograph of the excursions of tne can-U-.rx- -u.r ^^^^^^^^ 



sensitive plate movin. at the rate of ^ pp.h^ 1 ' "^^*^"«°\^ter as projected on a 

 torr variations " shown were dn! t V"'"^'''' P^^ ^^^<^<^^d. The four - excita- 



have probably seTTi^ T recen n^^h^ '7 v"; ''*^- ^^^'''•^ P^^-=^°' 

 photojraphs rccentlylken bTilTi'v of "^^ T ''^'t'l'^'^'" "^ 

 of birds. If the movpniAtTf ^f i '■ ^- ^' ' "''^ P^*^^* o^ 'lie Aieht 

 ^ill easily la^nTthaTw can ^t'TJ Tt P!^«*°?"phed, y^ou 

 movement as that of the XLtter1X,^"''-^T:^hre' 'TV 



J^e^rWeVThi'See^^'^nTrr' ^ ^^^^^^^i^ 

 (Fig' 10) which^ rS.'^terarHh'e^ ettricT/y^! A^*"^-^^ ? 

 successive excitations recorded by light wl^^^l^^^e^lSf 



