His evolution-related experiments and investigations led to books on orchids, "Insectivorous Plants, The Effects of Cross and Self Fertilisation in the Vegetable Kingdom", different forms of flowers on plants of the same species, and "The Power of Movement in Plants". He continued to collect information and exchange views from scientific correspondents all over the world, including Mary Treat, whom he encouraged to persevere in her scientific work. His botanical work was interpreted and popularised by various writers including Grant Allen and H. G. Wells, and helped transform plant science in the late 19th century and early 20th century. In his last book he returned to "The Formation of Vegetable Mould through the Action of Worms".