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 Rh to homologise the numerous pollen sacs either to grains of pollen which, bursting, liberated fovilla, or to male flowers, or to explain them in other ways, was not very successful. The fact is this was a piece of morphology for which the age was not ready. We must recollect that the comparative morphology of the ovule (in the wide sense) was not attempted, Brown's main contribution to the understanding of this structure consisted in the empirical accuracy with which he elucidated the actual structure—he made no attempt to frame a comparative morphology, for the simple reason that in the condition of knowledge at the time no such comparative morphology was possible or even dreamed of.

Two other remarkable discoveries now demand our attention, and both are instructive as shewing the keenness with which his highly trained powers of observation followed up the clues which his brilliant intellect had enabled him to descry. It was while engaged on a study of the Orchids and Asclepiads that he was led to recognise the existence of the cell nucleus. He worked almost exclusively with what we should call a dissecting microscope. One of his instruments is preserved in the Natural History Museum, and it is well to examine it and reflect on how much may be discerned even with a very primitive instrument if only a good brain lies behind the retina. The "microscope" contains a number of simple lenses of various powers, the highest about $1/32$" F.L. It is easy with such an instrument to see the nucleus in the epidermal cells when one knows it is there, but to have discovered it, and at a time when the technique of staining, &c., was simply non-existent, was a triumph of genius. Brown, of course, could not fully appreciate the great importance of his discovery, but he quite realised that he was dealing with no isolated or trivial fact, and, with characteristic industry and enterprise, he searched many other plants to find out whether his newly recognised nucleus was general or not; he found it to be so, and we all know how the discovery began at once to bear fruit.

A second observation to which I would refer was also of wide interest, and it was not made merely by chance. Brown was anxious to penetrate if possible into the secrets of fertilisation.