634 BOTANICAL TECHNIQUE 



potassium bichromate will not keep. Le Page's glue or Mayer's 

 albumen may replace the gum arabic solution. 



Syombathy's {Zeit. wiss. Mik., xxxiv, 1918, p. 334) gelatin 

 mixture is prepared by dissolving 1 grm. gelatin in 100 c.c. 

 distilled water at 30° C. Add 1 c.c. of a 20 per cent, solution of 

 sodium salicylate, shake well, cool and filter through cheese cloth. 

 Then add 15 c.c. pure glycerin. The mixture should be perfectly 

 clear. Rub 2 drops of the mixture and 2 drops of 2 per cent, 

 formalin on the slide, add the sections and straighten them. The 

 formalin renders the gelatin insoluble. Artschwager {Bot. 

 Gaz., Ixvii, 1919, p. 373) smears the slide with affixative and 

 floats the ribbons on 2 per cent, formalin solution. After they 

 are stretched, drain off the surplus water and allow to dry in a 

 thermostat in the presence of a small dish of formalin. 



Haupt's Modification [Staiii Tech., v, 1930, p. 97). Dissolve 

 1 grm. of gelatin in 100 c.c. distilled water at 30° C. Add 2 grm. 

 phenol crystals and 15 c.c. pure glycerin. Stir well and filter. 

 The phenol is a better preservative than sodium salicylate. Only 

 the best grade of gelatin must be used and the temperature 

 must not exceed 30° C. Gelatin which dissolves only at a higher 

 temperature is not satisfactory. If one to two days are required 

 for the gelatin to dissolve, decomposition commences, and if the 

 phenol is added too soon the undissolved gelatin turns white 

 and hardens. 



Barratt's Collodion-Clove Oil Affixative {Ann. Bot., xxx, 

 1916, p. 91) ; see also Bond {Trans. Roy. Soc. Edin., Ivi, 1931, 

 p. 695). A mixture of collodion and clove oil in the proportion 

 of 1:3 was used by Barratt. Bond used approximately equal 

 parts. Stretch paraffin ribbons on water on a slide lightly smeared 

 with glycerin to spread water evenly. Transfer the stretched 

 ribbons to a second slide smeared with the affixative. A slight 

 emulsion forms, but it is of no consequence. Allow at least twenty- 

 four hours to dry. The transfer of the ribbons is most easily 

 made with the aid of a pair of broad-tipped, blunt -ended forceps. 

 Grip one end of the ribbon and, with a lifting and pulling motion, 

 raise the ribbon from the water surface ; allow the end of the 

 ribbon furthest from the forceps to make first contact with the 

 second slide and then gently lower the remainder of the ribbon 

 into place. The method is especially valuable in permitting the 

 use of eau de Javelle for clearing sections attached to the slide ; 

 this reagent commonly destroys other affixing agents. 



Crabb {Science, Ixxx, 1934, p. 530) uses two solutions : (A) a 

 dilute solution of collodion in equal parts of alcohol and ether ; 

 (B) a mixture of 1 part amyl acetate with 4 parts of solution A. 

 Sjiread the sections and dry thoroughly ; flood with solution B 

 and leave face up on a level surface until the sections are free 

 from paraffin. Then blot vigorously with filter paper. Next 



