Chap, in.] of Cell- membrane in Plants. i- ti 



surface towards the object-glass, which shows that they did not 

 then use covering glasses. Nor was sufficient attention shown 

 to the use of sharp knives of suitable form, such as the razor. 

 which is now almost exclusively employed, or to practice in 

 making transverse and longitudinal sections of the utmost 

 possible delicacy,— two things which, through the example of 

 Meyen's and von Mohl's practice, were afterwards recognised as 

 indispensable helps to phytotomy ; even in their time observers 

 were satisfied with crushing and picking their preparations to 

 pieces. 



Drawing from the microscope kept even pace on the whole 

 with increasing skill in making preparations, and with the 

 improvement of the instrument. If we compare together the 

 drawings of Mirbel and Kurt Sprengel in the beginning of the 

 century, those of Link and Treviranus in 1807, Moldenhawer's 

 in 181 2, and Meyen's and von Mohl's from 1827 to 1840, we 

 shall obtain a rapid and instructive survey of the history of phy- 

 totomy during this period of forty years. The figures testify at 

 once to constant increase in the magnifying powers, to the 

 greater clearness of the field of sight, and still more to the 

 constant improvement in the arts of preparing and observing 

 objects. But a curious misconception crept in among the 

 phytotomists at this time ; they believed that more correct and 

 trustworthy figures would be obtained, if the observer and 

 writer did not himself make them, but employed other eyes and 

 other hands for that purpose ; they imagined that in this way 

 every kind of prejudice, of preconceived opinion would be elimin- 

 ated from the drawings. Thus both Mirbel and Moldenhawer 

 had their figures drawn by a woman, and many later phytotomists 

 entrusted the execution of their drawings to hired draughtsmen, 

 as Leeuwenhoek had done before them. A drawing from the 

 microscope, like every other copy of an object in natural 

 history, cannot pretend to take the place of the object itself, 

 but is intended to give an exact and clear rendering of what 

 the observer has perceived, and by so doing illustrate the 



s 2 



