—90— 



and have also learned that others have done the same. I quote 

 from the Revue Bryologique for 1893, M. Amann's remarks on 



this subject: 



"The employment of mica slides for the preserving in the 

 herbarium microscopic preparations of the organs of the mosses 

 was recommended in 1853 by Carl Mueller in his 'Deutschlands 

 Moose.' This eminent bryologist says in one of the numbers of 

 Natur that thanks to this method, which permits the comparison 

 under the microscope in a few minutes of the organs of a great 

 number of species, it has been possible for him to devote himself 

 to the systematic study of the mosses of the entire world. 



"In fact these microscopic preparations accompanying every 

 specimen in the herbarium and enclosed in the same envelope 

 with the specimen from which they were taken, permits a_ great 

 economy of time and are for that reason exceedingly convenient. " 



M. Amann objects to them, however, as dry mounts, because 

 of the imperfection of the image and because all our modern ob- 

 jectives are corrected for a standard thickness of cover-glass. He 

 therefore prefers to use a small slide, only 25 mm. long and H mm- 

 thick, which is specially made for anatomical preparations. As a 

 mounting medium he uses gum arable dissolved in glycerine jelly, 

 thinned with distilled water, to the thickness of honey. Specimens 

 transferred from either cold or hot water to this medium harden 

 in a few hours and preserve indefinitely, being less bulky than or- 

 dinary slides for microscopic preparations. — E. G. Britton. 



• 



My method of making microscopic slides is as follows: Dis- 

 sections are made in water on the stage of a simple microscope. 

 This stage is removable so that it can be placed under a compound 

 microscope and the smaller parts examined without disturbing 

 their position. Such parts as I wish to retain are transferred to a 

 few drops of dilute glycerine (10 to 20 per cent.) on a glass slide 

 on the end of which a number is marked with pen and ink for 

 means of identification. This is set aside without cover glass un- 

 til the water has entirely evaporated, leaving only clear glycerine. 

 It usually requires at least an hour, generally more, unless the 

 slide is placed where it will be warm (but not hot). 



I usually leave it over night when convenient. After this it 

 only remains to again transfer to hard glycerine jelly by almost 

 any of the methods in general use. For the "permanent" slide 

 and cover I now invariably use mica. The slides are fairly 

 stiff and from iK to 2 inches long by K or I wide, while the 

 covers are thinner and | by }i inch or larger, as the particular 

 case demands. These slides are placed in small envelopes glued 



