FD’s experiment shows that caustic does not interfere with the bending of radicles. Believes that the apex is a kind of brain for certain movements, being specialised to receive certain irritations.

Stresses importance of ensuring that cauterisation of radicles does not, through injury, prevent movement. Plans an experiment to test for "apheliotropism" in certain radicles.

Heliotropism nomenclature. Apheliotropic mustard roots grow more quickly in dark. Measures growth with microscope as S. H. Vines did in mould. Studying air roots.

FD’s and Stahl’s negative opinion of Sachs.

CD gives suggestions concerning FD’s experiments on the radicles of roots. Asks him to find out whether J. von Sachs tried beans. Should also try other gramineous plants.

Bernard looking forward to his father’s return.

Describes bean experiments. Will tell Emma Darwin to tell Elizabeth Darwin that he has written to the Riffel.

Pressure paralyses the streaming of protoplasm in the hairs of Tradescantia.

Notes observations on sensitivity and movement of radicles.

Has finished chapter [of Movement in plants] on sleeping plants and is now looking over heliotropism notes.

Is perplexed by Erasmus Darwin; Erasmus [A. Darwin] likes it, but Henrietta thinks it much too long.

Discusses Müller-Thurgau’s work on heliotropism. Will start on Thursday for Heidelberg and Strassburg.