_Electric test: Experiment 187._--By the end of August the geo-electric indications given by the probe had, as stated before, almost disappeared. The tonic condition of the specimen, _below par_, was independently revealed by the response to prick of the probe: this, in vigorous specimens, is by an electric response of galvanometric negativity. But the response to prick in sub-tonic specimens is very different. I find that when the physiological condition of the tissue falls _below par_, the sign of response undergoes a reversal into one of _galvanometric positivity_. The same reversal under condition of sub-tonicity was also shown to take place in growth, where under the stimulus of light a positive acceleration took place, instead of normal retardation of growth (p. 221). In the present investigation, the insensitive specimens were found to give abnormal positive electric response to the stimulus of prick made by the probe. The prick-effect in fact often gave me previous indication as to the suitability of the particular specimen for exhibition of geo-electric response. _Test of geotropic reaction: Experiment 188._--I took four different specimens of _Bryophyllum_ and _Nymphæa_, and held them horizontal. These plant organs had, earlier in the season, exhibited very strong geotropic effect, the shoot curving up through 90° in the course of ten hours or less. But these specimens obtained later in the season exhibited very feeble curvature, which hardly amounted to 10 degrees, even after prolonged exposure to geotropic action for 24 hours. _Test of microscopic examination._--I next made sections of _Bryophyllum_ and _Nymphæa_ and on examining them under the microscope discovered certain striking changes. A fortnight ago the group of large starch grains stained with iodine were the most striking feature of the starch sheath. But now these starch grains could not be found in any of the numerous specimens examined. The presence of the starch grains thus appears to be associated with the sensitiveness of the perceptive layer. REACTION AT LOWER SIDE OF THE ORGAN.