_Experiment 86._--I took a growing bud of _Crinum_ and determined the region of its growth activity; lower down a region was found where the growth had attained its maximum and may, therefore, be regarded as indifferent region. I applied two electrodes in this indifferent region about 1 cm. below the region of growth. On application of moderate electric stimulus of short duration the response was by an acceleration of growth which persisted for nearly a minute, after which there was a resumption of the normal rate of growth. In this particular case the interval of time between the application of stimulus and the responsive acceleration of growth was 12 seconds. The interval varies in different cases from one second to 20 seconds or more, depending on the intervening distance between the point of application of stimulus and the responding region of growth. I give a record (Fig. 81) obtained in a different experiment which shows in an identical specimen, (1) an acceleration of growth under Indirect and (2) a retardation of growth under Direct stimulus. [Illustration: FIG. 81.--Effect of Indirect and Direct stimulus on growth of _Crinum_, taken on a moving plate. Dotted arrow shows application of Indirect stimulus with consequent acceleration of growth. Direct application of stimulus at the second arrow induces contraction and subsequent retardation of rate of growth. Successive dots are intervals of 5″. (Magnification 2,000 times).] TABLE XIX--ACCELERATING EFFECT OF INDIRECT STIMULUS ON GROWTH (_Crinum_). +----------+--------------------------+--------------------+ |Specimen. | Condition of experiment. | Rate of growth. | +----------+--------------------------+--------------------+ |I | Normal | 0.21 µ per second. | | | After Indirect stimulus | 0.26 µ " " | +----------+--------------------------+--------------------+ |II | Normal | 0.25 µ " " | | | After Indirect stimulus | 0.30 µ " " | +----------+--------------------------+--------------------+ It is thus seen that the effect of Indirect stimulus on growth-variation is precisely parallel to that obtained with the response of sensitive plant; that is to say, the effect induced by a feeble stimulus applied at a distance from the growing region is a positive variation or acceleration of growth. The effect becomes converted into negative or retardation of growth when the stimulus is Direct, _i.e._, when applied to the responding region of growth; under intermediate conditions, the growth-variation I find to be diphasic, a positive acceleration followed by a negative retardation. This is found true not merely in the case of a particular form of stimulus but of stimuli as different as mechanical, thermal, electric, and photic.