Someone has affirmed that no man is greater than the age in which he lives. A cryptic utterance, savouring perhaps of a certain dash of impressionism, and not altogether false as it is assuredly not wholly true. If, however, we endeavour dispassionately to appraise the performance of the world's great (though perhaps we should exclude the few greatest) men we shall probably discover that the implied limitation is justified, at least in part, by history and experience. The fact is that hardly anyone can really penetrate far into nature's secret places without losing his way. The virgin lands of knowledge that lie beyond the area of contemporary possession are first invaded by those who can breach the barriers that oppose advance, for genius, by its wider outlook enables those who are endowed with it to recognise the weaker spots in these barriers, and thus to lead the attack. But the new territory, even after it is won, is ever surrounded by unknown regions, still waiting to be overrun when, but not until, the conditions for further expansion shall have been fulfilled. [Illustration: _Plate XI_ ROBERT BROWN (_circa 1856_)] At the beginning of the nineteenth century the time was ripe for such an addition of new territory to the regions of Botany already occupied at that period. In England, at any rate, the work inaugurated by Ray and others had become overshadowed by the authority of Linnaeus, and even on the Continent the effective advance of the science was for various reasons almost stayed. It is true that in France the Jussieus had started advance on fruitful lines, and others like De Candolle were endeavouring to feel their way through the maze of dimly comprehended relationships, but their efforts were obscured by the growing and fatal facilities for piling up mere catalogues of plants without the clues necessary to direct their energies into more profitable channels. As regards the flowering plants, there was, it is true, a groping after a partially perceived natural system, but the lower ranks of the vegetable kingdom formed, so far as scientific purposes were concerned, a _terra incognita_, and the attempts to elucidate the morphology of these groups in the light of the angiosperms were, as we now can see clearly enough, plainly foredoomed to failure. Facts were distorted and observations misinterpreted in ways that now seem to us almost to smack of sheer perversity, but we must not forget that the methods which in later years have proved so effective had not then been recognised; Hofmeister, with his marvellous genius, had not as yet arisen to shew the way through the maze of the lower forms. But what does strike one as astonishing, or might do so if the circumstance were not still so common, is the evidence of the difficulty men experienced in really seeing things as they were, and of distinguishing the fundamentally important from the trivial or even irrelevant.