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NOTES ON FISSIDENS 

 I. Difficulties in Determining the Oldest Species 



Elizabeth G. Britton 



The cut given above is taken from the title-page of Hedwig's Species Mus- 

 corum, published after his death, by Schwaegrichen at Leipzig in 1801. Several 

 interesting facts may be noted, first that it is a simple microscope, second that the 

 object appears to be dry, without slide or cover glass, and furthermore the plant 

 was evidently not much dissected. These Hmitations, will explain why even 

 'Hhe father of bryology' may have occasionally included more than one species 

 under one name! But, when we remember "Gray's Botanist's Microscope" as 

 advertised in the back of Gray's Manual as late as 1878 and our first compound 

 microscope, with two or three tiny objectives, and recall the blurry uncertain 

 images that resulted therefrom, we cannot help wondering at the artistic skill 

 and accuracy of many of the old plates published in the last part of the i8th and 

 the early part of the 19th centuries. 



The principle of the compound microscope was discovered as early as 1590 

 but no great improvement was made in it for over two centuries. All the earlier 

 English and French microscopes in the Cox collection, at the New York Botanical 

 Garden, showing the history of the development of the microscope, prove that a 

 very small objective with poor illumination, was in general use and the makers 

 seem to have striven to produce a small, portable and compact instrument, that 



