In 1880, Charles Darwin published The Power of Movement in Plants, a heavy volume of nearly six hundred pages in which he presented the results of many years of experiments conducted with his son Francis on the reaction of plants to the influence of light and gravity. His results contradicted the observations and explanations of the same phenomena offered by the German plant physiologist Julius Sachs in his influential Lehrbuch der Botanik (1868, English translation 1875). Darwin wished rather to ‘convert him than any other half-dozen botanies put together’. Sachs, however, regarded Darwin's work with contempt. Taking up the topic in his Vorlesungen über Pflanzenphysiologie in 1882 and taking issue especially with Darwin's experiments on the movement of root radicles in reaction to gravity, he remarked sharply: In such experiments with roots not only is great precaution necessary, but also the experience of years and extensive knowledge of vegetable physiology, to avoid falling into errors, as did Charles Darwin and his son Francis, who, on the basis of experiments which were unskilfully made and improperly explained, came to the conclusion, as wonderful as it was sensational, that the growing point of the root, like the brain of an animal, dominates the various movements in the root.