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 Rh more recent research. In appraising his work it must be remembered that he was essentially the pioneer of the science. It is true that some observations on plant anatomy occur in Robert Hooke's Micrographia, which was published six years before Grew sent in his first manuscript to the Royal Society; but Hooke never really attempted to make a systematic study of the subject. He had succeeded in greatly improving the microscope, and his chief interest was in applying his instrument to all kinds of bodies, vegetable and otherwise. Cork, charcoal, pith, etc., came under his observation, and to some extent he understood their structure. Grew acknowledges indebtedness to "the Learned and most Ingenious Naturalist Mr Hook" and tells us that some of the results which Hooke obtained, inspired him to study certain of his plants again with a better microscope. For instance Hooke was able to see smaller pores in wood than Grew had been able to detect, but, with better glasses, he confirmed the accuracy of Hooke's observation. However, although Hooke must certainly be credited with priority in the discovery of the fact that plant tissues are characterised by a cellular structure, his botanical work, considered in its entirety, is of very slight significance compared with that of Grew.

Grew's clearest account of plant cells is perhaps to be found in his description of root parenchyma, which he compares to "the Froth of Beer or Eggs" or to "a fine piece of Manchet ," or again, to "a most curious and exquisitely fine-wrought Sponge." He quotes with approval Hooke's description of Elder-Pith as "an heap of Bubbles" It would be unsafe however to conclude that he had really arrived at what is known as the Cell Theory. His conception of the nature of plant tissues was not by any means that of the modern botanist. He believed the cell-walls to consist of interwoven fibres, which were continuous from cell to cell. He did not consider that these fibres were invariably wrought together in such a fashion as to enclose bladder-like spaces, or cells; in some cases he held that the tissue was non-cellular, consisting simply of interwoven fibres. It was these hypothetical fibres, rather than the cells, which he