Page:The Journal of Indian Botany.djvu/172

142 THE JOUBNAL OF INDIAN BOTANY. found valuable for the study of yeasts. Hard potato agar (potato broth with 3 % agar and 2 % dextrose) is carefully cleared and stored in test tubes. When wanted for use, the agar is barely melted, and inoculated with a thick culture of yeast. A small drop of the suspension is spread evenly over a chemically clean warm slide, then incubated in a damp chamber at favourable temperature. When the colonies of yeast have reached the desired stage of development, they are killed and stained by any of the standard methods* Great care musf be exercised to prevent the agar him from floating off the slide. In practice it is better to leave one end out of the solutions so that the agar film may become dry. After staining, the film is dehydrated, cleared, and mounted in the usual manner. The great advantage is that the cells of the oolony are retained in their normal position, and are all in one plane

Goodspeed, T. H. Method of replacing paraffin solvent with paraffin. Bot. Gaz. 66 (1918) pp. 381-382.

For fine morphological and cytological preparations it is necessary that the material be infiltrated with paraffin very slowly. According to the method of the author, the vial of xylol containing the material is first cooled ; then melted paraffin is poured carefully over the surface.. When properly done the paraffin hardens into a well formed plug at the surface of the xylol, and shows no tendency to slip down later. Solution goes on slowly from the bottom of the plug, and infiltrates the material gradually.

Szombathy, Kolomon. Neue Methode zum Aufkleben von Paraffinschnitten (New methods of affixing paraffin sections). Zeit. Wiss. Mikr. 34 (1918) pp 334-336.

Sections of many kinds of material are difficult to keep on the slide during the various processes of staining. In the new methods the fixitive is made as follows: dissolve 1 gm. of gelatin in 100 cc. of distilled water at 30° C, add 1 cc. of a 2% solution of sodium salicylate, cool, and filter ; then add 15 cc. pure glycerine. Among the various methods for use, probably the most satisfactory is to smear the fixitive thinly on a clean slide, float the paraffin sections out on the slide in a 2% formalin solution, and gently warm on a warming plate to flatten them. Drain off the excess of formalin solution, and dry the slide. The fixitive keeps well, holds very refractory material on the slide even after prolonged washing in water, is not affected by alkalis, and shows little tendency to take up stains.

Otis, Charles H. Labeling of miscroscopical slides in staining technique. Science N. S. 47 (1918) pp. 219-220

To avoid the danger of loss or mutilation of labels on slides during stain, ing, the labels may be written at one with an ink made according to the following formula : dissolve 15 gms. of best cabinet maker's glue in 100 cc. of water at low temperature, add excess of potassium bichromate crystals, and expose to strong light for a week ; then filter, and rub in stick India ink to the desired blackness ; store in a tightly stoppered glass bottle. The ink keeps well, is easy to use, and is not affected by the usual reagents. An ordinary pen is used for writing and the slides must be clean.-

Gage, Simon H. Hand made lantern slides. Science N. S. 48 (7918) pp. 221-222.

Where it is desired to use hand drawings for lantern slides, they may be made quickly and satisfactorily by coating clean lantern plates with a thin