266 G. C. KAROP ON HANGING-DROP CULTIVATION. 



square covers, a soup plate and bell-glass to fit it, white blotting- 

 paper, and a strip or two of perforated zinc complete the outfit. 

 Cut the millboard into pieces 1 in. square, and punch out the 

 centres with a | or ^ gun-wad punch. Take a strip of perforated 

 zinc about 6 x 2| in., and bend down 1 in. of the longer diameter 

 at both ends to a right angle, thus making a table or support for 

 the slides to i-est upon while in the moist chamber formed by the 

 soup plate and bell-glass. 



We will now suppose some subject is ready for study ; and to 

 take the one suggested by the President's Address, let it be the 

 spores of a fungus. The first proceeding is to thoroughly soak 

 one or more of the punched squares of millboard in water ; and to 

 do this without resolving the material into its constituent layers, 

 the pieces should be put between two bits of glass lightly weighted 

 on the top and immersed for some hours. If a shallow drop only 

 is required, take one of the squares, if a deep one two or more, 

 and having squeezed out any excess of water place it, or two 

 superimjDosed, in the centre of a 3 X 1 slip. Now take a cover, 

 and ring a very thin smear of soft paraffin or vaseline just a 

 shade smaller than the aperture in the millboard. In a clean 

 capsule put a little of the nutrient fluid employed,* and stir in 

 the spores, mixing thoroughly ; now plant a moderately convex 

 drop of this in the centre of the ring with a glass rod or dropper, 

 and invert carefully over the perforation in the millboard ; there 

 is now a ' hanging drop ' on the underside of the cover. Place 

 three or four layers of blotting-paper on the bottom of the soup 

 plate with sufficient water to saturate them, on these the zinc 

 support, on this the slide with the hanging drop, and over all the 

 bell-glass. Note the time, and examine at some fixed intervals, 

 drawing all visible changes. On removal from the moist chamber 

 any condensation on the cover may be removed by snips of 

 blotting-paper, fixing it at one corner to prevent displacement ; 

 and during a prolonged examination under the microscope it may 

 be necessary to moisten the millboard with a camel-hair brush 

 dipped in water, to make up the loss by evaporation. 



In this elementary note I have not troubled about sterilisation, 



* For Coprophilous Fungi the best medium, I believe, is an infusion of 

 the dung on which they ordinarily grow. For some organisms, as Saccharo- 

 myces, etc., Cohn's or Pasteur's fluids are used, and for the "germination " 

 of pollen a 1-per-cent, cane-sugar solution is recommended. 



