Page:Life Movements in Plants.djvu/228

198 or growth. When the intensity of stimulus was raised to 3 units, there was illtillCt‘d an actual contraction.

It will thus he seen, that external stimulus of electric shock induct-s a reaction which is of Opposite sign to the normal growth elongation or expansion. We may con- veniently describe this ell'cct as ‘incipient’ contraction; for under lllUl‘t'tlHlIlg intensity of stimulus, the contractile function. opposing growth elongation, becomes more and more, pronouncml; at an intermediate stage this results in an arrest of growth; at the further stage, it culmin- m'os in an actual shortening of the organ. There is no hrvuk of continuity in all these stages. I shall, therefore, use the term ‘contraction’ in a wider sense, including the ‘incipivut’ which linds expression in a retardation of growth.

In Table XVI is gin-n the results of certain typical experiments on tho cll'oct of stimulus of increasing intcn- sity and duration.

'r.\m.ic xv1.—~-inooct:'r or m'rszisi'n' AND DURATION or ELEU'I‘RH‘ srmmns N tllct‘tW'l‘ll.

l Duration of i I . ‘. . : nt -n." . '. n. i - ‘, Appllt'illltill. j I ( 5“) 1h“ or glmml‘ I __ - _ _ _ _ l Normal 0-35 It per second. _ 5 seconds  1 unit  0-22 ,u ” n ,.  2 units  (H)? 'u, ,, ,, ,.  '1 n  Arrest of growth. . Normal  0'30 [1. per second. (‘ontinnons stnnu- (in) unit  0-20 F ” ” ' lation ; , l . ' ! ’, ; .‘l 9, no. I  ,1 ,, E ,, . .5 ,.  ‘ (.ont ‘actlon.