+-----------+-----------------------+-------------------+ | Specimen. | Hydrostatic pressure. | Rate of growth. | +-----------+-----------------------+-------------------+ | | Normal | 0.18 µ per second.| | No. I | 2 cm. pressure | 0.20 µ " " | | | 4 cm. " | 0.11 µ " " | | | | | | | Normal | 0.13 µ " " | | No. II | 1 cm. pressure | 0.20 µ " " | | | 3 cm. " | 0.18 µ " " | | | 4 cm. " | 0.15 µ " " | +-----------+-----------------------+-------------------+ RESPONSE TO NEGATIVE VARIATION OF TURGOR. I shall now describe the influence of induced diminution of turgor on the rate of growth. [Illustration: FIG. 71.--Effect of alternate increase and diminution of turgor on the same specimen: N, normal rate under drought; H, enhanced rate under irrigation with warm water; N′, normal permanent rate after irrigation; P, diminished rate after plasmolysis (_Zephyranthes_).] _Method of plasmolysis: Experiment 72._--Being desirous of demonstrating the responsive growth variations of opposite signs in an identical specimen under alternate increase and diminution of turgor, I continued the experiment with the same peduncle of _Zephyranthes_ in which the growth acceleration was induced by irrigation with warm water. In that experiment the growth rate of 0.04 µ per second was enhanced to 0.20 µ per second after irrigation. A strong solution of KNO_{3} was now applied at the root; and the growth-rate fell almost immediately to 0.03 µ per second, or nearly to one-third the previous rate, the depression induced being thus greater than under condition of drought (Fig. 71). TABLE XIV.--EFFECT OF ALTERNATE VARIATION OF TURGOR ON GROWTH (_Zephyranthes_). +--------------------------------+-------------------+ | Condition of Experiment. | Rate of growth. | +--------------------------------+-------------------+ |Dry soil | 0.04 µ per second.| |Application of warm water | 0.20 µ " " | |Steady growth after 1 hour | 0.08 µ " " | |Application of KNO_{3} solution | 0.03 µ " " | +--------------------------------+-------------------+ From the series of results that have been given above, it will be seen that employing very different methods of turgor variation, the rate of growth, within limits, is enhanced by an increase of turgor. A diminution or negative variation of turgor, on the other hand, brings about a retardation or negative variation in the rate of growth. We should, in this connection, bear in mind the fact that, growth is dependent on protoplasmic activity, and the variation of turgor itself is also determined by that activity.