Here we see how much light may be thrown on animal structures and functions by vegetable physiology. We learn to limit our ideas of the superiority of animals by discovering how much of what we consider peculiar to them is found in plants. We appreciate the unity of biology, indivisible without injury to our knowledge of its parts. No structure in plants appears more wonderful, as Darwin describes it, than the tip of the rootlet of a seedling. It is impressed by and transmits influences of pressure, injury, moisture, light, and gravity to other parts, and determines the course pursued by the rootlet in penetrating the ground. "It is hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals;" and the brain of Charles Darwin, in working out this acquisition of knowledge for mankind, has added a new department to vegetable physiology and to biology. CHAPTER X. In his later years honours poured thick upon Darwin. In 1871 he received the Prussian order of knighthood "For Merit"; and was elected a corresponding member of the Austrian Academy of Sciences. In 1877 Cambridge University, making an exception to its custom of not conferring honorary degrees on its members, gave him the LL.D. and an ovation, when the kindly eyes of the venerable naturalist beamed upon the monkey-figure dangled by undergraduates before him from the galleries, in addition to a solitary link of a huge chain, no doubt representing "the missing link." In 1878 the honour, long withheld, and certainly unsought, of being elected a corresponding member of the Paris Academy of Sciences in the section of Zoology, was his; and that tardy body recognised late the man whose supremacy in science it had done nothing either to foster or to approve. In 1879 the Baly Medal of the London College of Physicians was awarded to him. After the Cambridge celebration a subscription was raised to obtain a portrait of the veteran evolutionist, which was executed by Mr. W. B. Richmond, and now adorns the Philosophical Library of the New Museums at Cambridge. Later, yet another portrait--the finest in his own and many others' belief--was painted by Mr. John Collier, and presented to the Linnean Society, which will always be associated with the first announcement of Darwin's main theory, as well as with many others of his scientific discoveries.