568 SUMMARY OF CURRENT RESKARCHES RELATING TO 



may be kept warm and at fairly constant temperature for at least 24 hours, 

 until a base of supplies can be reached. The principle of a fireless 

 cooker, with a few modifications, has been made use of. The insulating 

 portion is a box composed of pressed cork, 2 in. thick. Over this is fitted 

 a cover of the same material. The box is hned with heavy felt. Within 

 is a copper water jacket to hold water at any desired temperature. The 

 cultures are placed in a wire cage which just fits into the water-jacket. 

 The whole outfit is again made to fit into a leather case, with a handle 

 and straps. The weight is about 2:-! lb. 



Preservation of Plate Cultures.* — E. G. Hastings describes a 

 simple and satisfactory method for the preservation of plate cultures for 

 museum and demonstration purposes. Some ordinary thread agar is 

 immersed for several days in changes of tap-water to remove the 

 materials which give turbidity to solutions of agar. By this treatment 

 the agar is rendered so pure that a 1 p.c. solution is nearly as trans- 

 parent as glass. A 2 p.c. solution of this agar is prepared by dissolving 

 in distilled water and filtering through paper. To this is added an 

 equal volume of glycerin. No sterilization is necessary. To preserve 

 an ordinary plate culture it is only necessary to melt some of this 

 glycerin agar, cool to 45° C. and pour carefully over the surface of the 

 plate culture. The glycerin is sufficiently hygroscopic to prevent 

 shrinking of the medium. If desired the plate cultures may first be 

 hardened by exposure to formalin vapour. Gelatin plates so hardened 

 are not melted by the warm glycerin vapour. Liquefying colonies on 

 gelatin may be preserved, if the formalin treatment is continued for 

 long enough to destroy the enzymes, though in this case satisfactory 

 preparations are not always obtained. Plate cultures preserved by this 

 method remained in perfect condition after eight months. It is not 

 necessary to seal the Petri dish in any way. 



(.3) Cutting-, including- Embedding and Microtomes. 



Embedding Minute Objects.f — When it is necessary to embed objects 

 of such minuteness that they cannot be picked up with a forceps, the 

 necessary manipulations are sim])lified l)y the use of a 1 p.c. solution of 

 agar. H. Fischer points out that fixing processes can be performed 

 either before or after the application of agar, but recommends that a 

 more highly concentrated agar be used if acids are to be applied, as agar 

 is rendered soft by acids. The objects to be dealt with may be added 

 to the melted agar in a watch-glass, after it has cooled to 40° C. Shaking 

 will prevent the objects sinking to the bottom of the agar. The thin 

 hiyer of agar does not affect cutting or staining processes. Any stain 

 taken up by it may easily be washed out. 



Cutting Sections without Embedding.^ — K. Peche describes 

 methods whereby sections may be obtained of botanical specimens which 



* Centralbl. Bakt., 2te Abt., xxxiv. (1912) pp. 432-4. 



t Zeitschr. -wiss. Mikrosk., xxix. (1912) p. 66. 



i Zeitschr. -wiss. Mikrosk., xxix. (1912) pp. 58-62. 



