It might be thought that such drafts as these upon the time and energies of a scientific man would leave no opportunity for other duties. But it was while burdened with the directorship that Sir Joseph was called to the highest administrative office in science in Great Britain. He served as President of the Royal Society from 1873 to 1878. The obligations of that position are far from being limited to the requirements of the Society itself. The Government of the day has always been in the habit of taking its president and officials into consultation in scientific matters of public importance. In these years the administrative demands upon Sir Joseph were the greatest of his life. They are marked by a temporary pause in the stream of publication. None of his own larger works belong to this period. It happens only too often in this country that our ablest men are thus paralysed in their scientific careers by the potent vortex of administration. Not a few succumb, and cease altogether to produce. They are caught as in the eddy of the Lorelei, and are so hopelessly entangled that they never emerge again. They fail to realise, or realise too late, that the administration of matters relating to a science is not an end in itself, but only a means to an end. Some, the steadfast and invincible seekers after truth, though held by the eddy for a time, pass again into the main stream. Hooker was one of these. The Presidency of the Royal Society ended at the usual term of five years. Seven years later he demitted office as Director of Kew. He was thus free in 1885, still a young man in vigour though not in years. For over a quarter of a century after retirement he devoted the energy of his old age to peculiarly fruitful scientific work. Thus the administrative tie upon him was only temporary. So long as it lasted he faithfully obeyed the call of duty, notwithstanding the restrictions it imposed. No exhaustive catalogue need be given of the works upon which the reputation of Sir Joseph Hooker as a _scientific systematist_ was founded. It must suffice briefly to consider his four greatest systematic works, _The Antarctic Flora_, _The Flora of British India_, _The Genera Plantarum_, and the _Index Kewensis_.