Journal of Applied Microscopy. 469 



should then be placed in equal parts of glycerine and 95 per cent, alcohol, where 

 it may be kept indefinitely. 



In cutting, the knife should be set as obliquely as possible, and both the 

 knife and the object should be kept wet with the mixture of glycerine and 

 alcohol. The sections are transferred to 70 per cent, alcohol as fast as they are 

 cut. The succeeding steps are the same as for free-hand sections, but many 

 stains are not available because they stain the celloidin. Safranin and Dela- 

 field's haematoxylin, or Delafield's haematoxylin and eosin are good combinations 

 for celloidin sections. Do not use absolute alcohol for dehydrating, since it 

 dissolves the celloidin, but transfer from 95 per cent, alcohol to Eycleshymer's 

 clearing fluid (equal parts of bergamot oil, cedar oil, and carbolic acid), which 

 clears readily from 95 per cent, alcohol. Mount in balsam. 



The celloidin method has its disadvantages as well as its advantages. It is 

 extremely slow and tedious, and it is rarely possible to cut sections thinner than 

 10 pi, while, on the other hand, it gives smoother sections. The entire absence 

 of heat makes it very useful for delicate, succulent tissues. Stems and roots 

 which cannot be handled at all in paraffin, cut well in celloidin, and much larger 

 sections can be cut than in paraffin. 



When material is to be imbedded, use celloidin as a last resort. Use paraffin 

 when you can, celloidin when you must 



I am indebted to my friend Mr. W. B. MacCallum for several suggestions 

 in regard to this method. 



THE GLYCERINE METHOD. 



It is hard to get the filamentous algae and fungi into balsam without shrink- 

 ing ; consequently, these forms are usually mounted in glycerine or glycerine 

 jelly. 



Flemming's fluid and chromo-acetic acid are good fixing agents. Corrosive 

 sublimate in water, or in TO per cent, alcohol, used hot, is also to be recom- 

 . mended. For general morphology, stain for six hours or over night in a one- 

 half per cent, aqueous solution of eosin, transfer directly to a 1 per cent, 

 solution of acetic acid in distilled water, and allow it to act for about five 

 minutes, wash thoroughly in water to remove the acid, and then put the material 

 into a watch glass in a 10 per cent, solution of glycerine in water. The watch 

 glass should be kept as free from dust as possible, and should not be covered. 

 As soon as the solution appears to be about as thick as pure glycerine the 

 material is ready for mounting. Place a small quantity of the material on a 

 slide, arrange it carefully, add a small drop of glycerine, and a round cover. 

 Seal with gold size (a varnish used by painters in laying gold leaf). None of 

 the sealing media will stick to moist surfaces, hence it is essential that there 

 should be only enough glycerine to come to the edge of the cover. If it is 

 desired to mount rather large specimens, like the antheridia, and the oogonia of 

 C/iara, it is best to spin a ring on the slide, thus forming a shallow cell. 



If glycerine jelly is to be used, place the bottle in warm water until the jelly 

 becomes liquid, but avoid any unnecessary heat. Take the material from the 

 glycerine, add a drop of the warm jelly, and seal as before. 



