Discusses heliotropism in plant cotyledons. Asks for information.

Did not wish to imply that some leaves are insensitive to light, only that he could not measure their sensitivity. Contraction of roots seems common.

Experiments to determine mechanism of tendril curvature; importance of variations in cell turgidity. Contraction in roots caused by increased turgor.

Thanks for letter.

Comments on growth and movement of plants.

Force of turgor is true cause of movement in plants. HdeV hopes to identify the substance which increases the cell’s water-absorbing power.

Perhaps movement from side to side in plants is caused by the contraction of one side, rather than the expansion of the other.

Sends seeds of Lychnis Githago: he observed the hypocotyledenous stem, not the root, contracting.

Movement of tentacles of Drosera.