8 VEGETABLE ORGANOGRAPHY. 



facts. For fear of seeing these discrepancies multiplied, 

 we conclude by distrusting our own eyes, and by fearing 

 to affirm any thing concerning what we believe we have 

 seen. I shall endeavour to develope on this occasion, 

 with all the caution which the obscurity of this part of 

 the science demands, what appears to me most worthy 

 of attention. I shall report with care the opinions of 

 various observers, in order to endeavour to understand 

 well those points upon which a difference exists, and 

 those upon which they are agreed. But before entering 

 into this exposition of the doubts and the uncertainties 

 of microscopic anatomy, I would first inform beginners, 

 that these doubts have much less influence than miofht 

 be believed upon the whole of the science. I will also 

 say, in concluding these preliminary observations, that 

 the precautions which have always proved the most 

 sure for avoiding microscopic illusions, are — 



First, Never to observe an object of considerable size, 

 without having commenced the observation with glasses 

 of weaker power, — so as to follow it in a gradual manner 

 from the lowest to the highest degree of enlargement. 



Secondly, To view the same object with microscopes 

 of different constructions, so that one may destroy any 

 illusion which another may have produced; by these 

 precautions the number of facts wliicli are affirmed is 

 perhaps slightly diminished, but more certainty is given 

 to them. 



When a transverse section of a plant, or a part of one, 

 reduced to a thin and transparent slice, is examined first 

 with a lens, and afterwards with a microscope, we per- 

 ceive unequal cavities, sometimes round or angular, and 

 most frequently hexagonal. If a longitudinal section 

 be made, we always find the cavities closed by dia- 

 phragms; frequently there are other tubular cavities 

 without transverse divisions, and sometimes widely 



