1900] MICROSCOPICAL JOURNAL. 195 



Diatoms. — To prepare photo-micrographs of diatoms, 

 first photograph the diatoms with a magnification of not 

 more than TOO diameters, then enlarge so as to ohtain a 

 photograph of 500 diameters, proper for photo-printing. 

 The finest details are thus brought out, which otherwise 

 are invisible to the eye in the smaller photograph. Even 

 forgeries in legal documents can be discerned by using 

 enlargement pictures, which microscopically are not vis- 

 ible if printed on bromide or velox paper. 



Fish-teeth. — The following method of preparing sec- 

 tions of the teeth of fish is suggested by Mr. A. Under- 

 wood, of the Leicester Square Dental Hospital. Sections 

 of fishes' teeth should not be ground, but the jaws and 

 teeth should be decalcified in a 5 per cent solution of 

 chromic acid, or a 10 per cent solution of hydrochloric 

 acid. After sections have been cut and stained, they 

 should be well washed in distilled water, dehydrated for 

 three minutes in absolute alcohol, cleared in oil of cloves, 

 and mounted in Canada balsam. Carmine is the best 

 stain for fishes' teeth. 



Fungi. — In collecting any fleshy fungi, care should be 

 taken to obtain all the fleshy structure, as some of the 

 most important characters are only to be observed in the 

 basal parts. To remove the basal portion entire, a knife 

 or small trowel should be employed. Specimens that are 

 broken off short with the ground are seldom of much value 

 for scientific purposes. Fleshy ascomycetous fungi can 

 best be preserved in alcohol, but many of them may also 

 be satisfactorily dried. It is well, when fungi gathering, 

 to take a stock of tissue paper to wrap the specimens in. 

 Each form should be wrapped up separately so as to pre- 

 vent breaking, or soiling from contact with one another. 



Dead Black. — A good dead black for varnishing the 

 interior of microscope tubes and cameras may be made by 

 mixing two grains of lamp-black with just enough gold 



