538 Journal of Applied Microscopy. 



As a usual thing the material is preserved in formalin a few days before 

 it is mounted up. This enables the coloring matter to become extracted, and 

 when permanently mounted in the jar does not discolor the formalin. 



When specimens are ready to mount, they are placed on a piece of ordinary 

 glass cut so as to fit the jar which is to hold them. A piece of bibulus paper 

 will take up the extraneous formalin adherent to the specimens ; and after this 

 has been done, a solution of gelatin, which hardens quickly upon cooling, is 

 poured over and around the specimens until they are quite well embedded. After 

 the gelatin has hardened, the specimens and their various parts may be labeled. 

 We make use of printed labels, which are easily put on by covering them with 

 a drop of transparent gelatin (see Figs. I, II, and III). 



The specimens now mounted upon glass are ready to be placed in the jar of 

 formalin, but in most instances we harden the gelatin still more ; or, more 

 properly speaking, dehydrate it by flooding the specimen for about five minutes 

 with ninety-five per cent, alcohol. The gelatin is dehydrated and hardened still 

 further when placed in the formalin. 



When some opaque background is placed behind the specimens the gelatin is 

 undiscernable. For the purpose of a background we use opaque black or white 

 glass cut the same size as that upon which the specimens are mounted, although 

 the specimens can be mounted directly upon opaque glass of any suitable color 

 if desired. 



Figures I and II show specimens put up in this manner, representing the 

 morphology of the seed, and the more important stages of germination of the 

 white lupine and sunflower. These specimens are representative of numerous 

 types which we have prepared, and they can be made of considerable value in a 

 laboratory of botany, especially in high schools where considerable attention is 

 now paid to the morphology of seeds. When placed in a round glass jar with clear, 

 clean glass, the details come out much more prominently than is shown in the 

 photograph. 



There is a considerable amount of material which can be mounted up and 

 properly labeled, for illustrating features of especial interest in a modern botanical 

 course. A large amount of pathological material might be advantageously shown 

 by this method, inasmuch as in many instances the formalin does not affect the 

 natural color pigments which are characteristic of many specimens. When the 

 pigment is removed by formalin, as in the case of mushrooms, etc., the speci- 

 mens can be painted with water colors, coated with gelatin, and the natural tints 

 are thus retained. Waterproof India ink and most water colors are not affected 

 by formalin. This method of preserving highly colored material has been used 

 somewhat by the writer with successful results. 



Another convenient method of preserving pathological material, especially 

 diseased leaves, is by mounting them between two small plates of glass in glyc- 

 erine formalin jelly, and covering the edges with paper to preyent evaporation, 

 in much the same manner as lantern slides are mounted. This method retains 

 the natural color of the specimens exceedingly well and is convenient for illus- 

 trating the various spot diseases of leaves (see Fig. IV). 



Of especial value in teaching botany is the preserving and use for illustration 



