628 BOTANICAL TECHNIQUE 



brittle objects. Dehydrate to absolute alcohol and clear in methyl 

 benzoate (instead of benzol) until material is infiltrated and sinks. 

 Treat two to five days, according to size, with 1 per cent, celloidin 

 in methyl benzoate. Replace with methyl benzoate to which 

 paraffin chips have been added and leave twelve to twenty-four 

 hours at 40° C. Finally place the objects in melted paraffin at 

 50° C, changing this paraffin at least three times, and imbed. 

 Avoiding benzol, chloroform and xylol prevents hardening and 

 shrinkage. 



Stehli and Kolumbe (Handb. der mikr. Tech. Aht., xii, 1929) 

 also give a method of imbedding in a mixture of paraffin and 

 celloidin. See also de Zeeuav, Papers Mich. Acad., Sci. i, 1923, 

 p. 83 ; Church, Science, xlvii, 1918, p. 640 ; Kornhauser, 

 Science, xliv, 1916, p. 57 ; Dahlgren, J. Appl. Micr., i, 1898, 

 p. 67. 



1247. Gelatin methods should be used for diseased bark and 

 wood that is likely to crumble and become brittle in paraffin or 

 collodion imbedding and for material that would be excessively 

 hardened in alcohol. The method of Nicholas (§ 180) is most 

 suitable. Following Land {Bot. Gaz., lix, 1915, p. 400), soak 

 gelatin in water until no more is imbibed. Drain off the excess 

 water and liquefy the gelatin by heat. Place pieces of the material 

 in the melted gelatin for several hours, together with small blocks 

 of hard wood to act as supports in the microtome. Orient the 

 material on the wooden blocks in a gelatin matrix, cool to set the 

 gelatin and plunge into strong formalin to harden it. 



See also Collazo, La inclusion, en gelatina. Montevideo, 1927 ; 

 HiRiNGA, C. B. Soc. Biol., xci, 1924, pp. 671 and 951. 



If the sections are strong enough, remove the gelatin with warm 

 water with or without a little ammonia. Otherwise mount in 

 glycerin jelly. 



1248. Jeffrey's Glycerin Jelly Mass Method of Imbedding 

 {Bot. Gaz., Ixxxvi, 1928, p. 458). The method is valuable for 

 cutting large numbers of small objects in a predetermined plane. 

 Dehydrate the material to strong alcohol and then transfer to 

 equal parts alcohol and glycerin and leave overnight. Arrange 

 the objects as desired, under the low power of a dissecting micro- 

 scope, on a strip of heavy paraffin paper in a small drop of alcohol 

 glycerin and leave it in a warm place to concentrate. Invert the 

 strip of paraffin paper bearing the objects on to a strip of cardboard 

 spread with melted glycerin jelly (dissolve one part of gelatin 

 in six parts of water and then add an equal volume of glycerin). 

 Place a small slide and a small weight on top. When the jelly 

 has set {^ hour), place in 90 per cent, alcohol to harden. Later 

 remove the paraffin paper and imbed the jelly strip in nitro- 

 cellulose. No doubt the method could be adapted to paraffin 

 imbedding. 



