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Smithia Pfundii.--The stiff terminal shoots of this Leguminous water-plant
from Africa project so as to make a rectangle with the stem below; but this
occurs only when the plants are growing vigorously, for when kept in a cool
place, the summits of the stems become straight, as they likewise did at
the close of the growing season. The direction of the rectangularly bent
part is independent of the chief source of light. But from observing the
effects of placing plants in the dark, in which case several shoots became
in two or three days upright or nearly upright, and when brought back into
the light again became rectangularly curved, we believe that the bending is
in part due to apheliotropism, apparently somewhat opposed by
apogeotropism. On the other hand, from observing the effects of tying a
shoot downwards, so that the rectangle faced upwards, we are led to believe
that the curvature is partly due to epinasty. As the rectangularly bent
portion of an upright stem grows older, the lower part straightens itself;
and this is effected through hyponasty.


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