+-------------------------------------------+ |Position of the| Geo-electric excitation | |probe. |(galvanometric negativity).| +---------------+---------------------------+ | Surface | 5 divisions. | | 0·4 mm. | -20 " | | 0·8 " | -24 " | | 1·2 " | -22 " | | 1·6 " | -18 " | | 2·0 " | -14 " | | 2·4 " | -10 " | | 2·8 " | -5 " | | 3·2 " | 0 " | +-------------------------------------------+ The results given above, typical of many others, show that there is a definite layer in the tissue which undergoes maximum excitation under the stimulus of gravity, and that this excitation irradiates with diminishing intensity in radial directions inwards and outwards. _The geo-perceptive layer may thus be experimentally localised by measuring the depth of intrusion of the probe for maximum deflection of galvanometric negativity._ _Localisation of geo-perceptive layer in_ Nymphæa: _Experiment 186._--I employed the same method for the determination of the perceptive layer of a different organ namely, that of the flower stalk of _Nymphæa_. The electric reaction in _Nymphæa_, even under the prevailing unfavourable condition of the season, was moderately strong, being about three times greater than in _Bryophyllum_. A dozen observations made with different specimens gave very consistent results of which the following may be taken as typical. The probe was in this case, as in the last, moved by steps of 0·4 mm. at a time. Other examples will be given later where readings were taken for successive steps of 0·2 mm. TABLE XLI.--SHOWING THE DISTRIBUTION OF INDUCED GEO-ELECTRIC EXCITATION IN DIFFERENT LAYERS (_Nymphæa_). +--------------------------------------------+ |Position of probe.|Galvanometric deflection.| +------------------+-------------------------+ | Surface | 0 divisions. | | 0·4 mm. | -16 " | | 0·8 " | -42 " | | 1·2 " | -20 " | | 1·6 " | -10 " | | 2·0 " | -2 " | | 2·4 " | 0 " | +--------------------------------------------+ It will be seen that as in _Bryophyllum_, so in _Nymphæa_, the geo-electric excitation increased at first with increasing depth of the tissue till at a depth of 0·8 mm. of the particular specimen the induced excitation attained a maximum value. The excitatory effect then declines till it vanished at a depth of 2·4 mm.