Robertson: The Plant Cell. i8i 



Worthy Person .... Mr. Hooke shevveth us, that the Pores of 

 the Pith, particularly of Elder-Pith, as far as they are visible, 

 are all alike discontinuous, and that the Pith is nothing- else 

 (to use his own words) but an Heap of Bubbles.' Respect, 

 however, is singularly wanting in Grew's treatment of the un- 

 fortunate engraver who executed his illustrations. To one of 

 the figures in his book called ' An Idea of a Phytological History 

 Propounded,' he appends the concise note, 'This sculpture is 

 utterly false ! " 



It is perhaps hardly surprising that even after making such 

 a good start, Cytology remained dormant, or else spent its time 

 in mistaken speculations, right through the eighteenth century, 

 since that century was in so many other ways a time of intel- 

 lectual barrenness. The great botanist Hugo v'on Mohl, who 

 flourished in the first half of the nineteenth century, says ' The 

 works of the plant anatomists of the eighteenth century did not 

 further the knowledge of cell tissues in the smallest degree.' 

 Some of the botanists of the period, seeking an analogy with 

 animal cellular tissue, fell into the error of describing vegetable 

 cellular tissue as a mass of irregular fibres and lamellae inter- 

 woven together ; whilst others regarded it as a homogeneous 

 mass hollowed into holes and canals. 



It was not until the nineteenth century that the study of the 

 cell obtained a new lease of life, chiefly through the exertions of 

 Hugo von Mohl, Robert Brown, Schwann, and Schleiden. We 

 may perhaps connect this renaissance with the fact that Amici 

 and Fraunhofer made the first achromatic objectives in 1815 — 

 an immense advance in the development of the microscope. In 

 1828 von Mohl in a brilliant paper elucidated the nature of pitted 

 membranes, and three years later Robert Brown discovered the 

 nucleus, the central organ of the cell which presides over all its 

 activities. The nucleus is so extraordinarilv important in 

 Cytology that I think it is worth while to quote the words in 

 which Brown announced his discovery. The passage occurs 

 incidentally in a paper on the Orchideae. ' In each cell of the 

 epidermis of a great part of the family, especially of those 

 with membranaceous leaves, a single circular areola, generally 

 somewhat more opake than the membrane of the cell, is 

 observable. This areola, which is more or less distinctly granular, 

 is slightly convex, and although it seems to be on the surface, is 

 in reality covered by the outer lamina of the cell. There is no 

 regularity as to its place in the cell ; it is not infrequently, 

 however, central or nearly so ... . This areola, or nucleus of 



1906 June I. 



