INTRODUCTION AND HISTORICAL BACKGROUND 5 



of the first importance in cellular organization which was not universally 

 accepted for more than a hundred years after his pubUcations. 



Advances following improved techniques 



The eighteenth century was generally one of stagnation in plant 

 morphology, and even of retrogression as far as wall studies were 

 concerned. Attention was centred around physiological problems, and 

 such details of anatomy as were needed were all too frequently taken 

 bodily from Crew's work. We may perhaps note what seems nowadays 

 a peculiar notion put forward by Wolff (1159) that the young parts of 

 plants consist of a transparent gelatinous substance, in which drops of 

 sap are secreted which grow into cells. The lamina separating two cells 

 he therefore regarded as single— an error which was to take many years 

 to eradicate. While this was undoubtedly an honest attempt to make 

 something out of the much more difficult softer plant tissues and was 

 occasionally revived even at a much later date, we cannot but regard 

 it, in the light of the elegance of Malpighi and the scrupulous care of 

 Grew nearly a hundred years earlier, as misinterpretation of faulty 

 observations. It formed the first denial of the fibrillar hypothesis. 



Further development had to await improvements in microscope 

 design and technique and these were not forthcoming until the first 

 quarter of the nineteenth century. During the period from 1812 to 1828 

 Selligue and Amici produced achromatic and aplanatic objectives with 

 three double lenses, and with these new instruments progress became 

 very rapid. 



Moldenhawer (the younger) used maceration techniques, and saw for 

 the first time whole cells separated from their neighbours. This brought 

 him immediately into conflict with Mirbel who (1801) had supported 

 the earlier notions of Wolff. Again with Moldenhawer we revert in some 

 degree to the "fibrillar hypothesis", since he considered the cells to be 

 held together in tissues by a matrix of finely woven fibres, which indeed 

 he claimed actually to have seen. This reversion culminated with 

 Meyen who visualized cell construction very much in the way Grew 

 had done. We may perhaps note in passing that Kieser (1815) examin- 

 ing the problems of cell shape which have been a subject of investigation 

 even in the most recent times, pointed out (almost correctly) that all 

 cells were fundamentally rhombic dodecahedra. 



Undoubtedly the greatest figure of this period, however, was von 

 Mohl. He gave what amounts to the modern view both on the primary 

 and the secondary walls of cells {see Chapter II) though he misunder- 

 stood the bordered pit, and one feels in his work, perhaps for the first 



