696 



ADDITIONAL EXERCISES 



Several solid culture media recommended by Lindner can be used in the growth 

 of various moulds in test-tubes and in Petri dishes for class use. Such is grape juice 

 exactly neutralized and combined with 10 per cent, gelatin. .Another medium is 

 prepared by taking i liter of white wine, heating it over a flame for one-half hour to 

 drive off completely the alcohol. The liquid lost by evaporation is replaced to bring 

 the volume up to i liter. It is neutralized exactly and 10 per cent, gelatin is added. 

 On fhi'; medium moulds grow luxuriantly. The gelatin can be replaced by agar- 

 agar, using 1.3 per cent., and the advantage of tbi'a medium is that it does not 

 liquefy. The writer has found baker's bread a useful medium for the growth of 

 moulds under bell jars, the air of which is kept moist by filter paper. If the bread 

 is used in Petri dishes, it can be sliced, cut into a circular form, soaked in ivater, or 

 beerwort, placed under cover in the Petri dish, which should then be sterilized one 

 or two times. He has found beerwort agar extremely useful in raising moulds and 

 other filamentous fungi. .A supply of the -|- and — races of heterothallic moulds 



9 



Pig. 240. — Forms of columella, a. Spheric; b, spheric with collarette; c, oval; d. 

 depressed oval; e, piriform; /. panduriform; g. conic; h, cylindro-conic; i. mammiform; 

 k. I. spinescent. (After Lendner.) 



should be kept in culture, so that the students may experiment with the formation 

 of the gametes and zygospores. These can be mounted in acetic acid with a ring 

 of asphalt about the cover-glass, or they can be fixed and carried up through the 

 alcohols to such materials as \'enetian red in which they are not onlv beautifuUv 

 stained, but also keep indefinitely. The Venetian red can be softened in a water 

 bath and a little placed in the center of a slide with the addition of a little balsam 

 to fill out the space beneath the cover. 



The systematic study of the moulds should begin after their general morphology 

 and phj-siology have been considered. Cultures, the names of which are known to 

 the teacher, should be then given to the members of the class in mycology, as un- 

 known moulds, which the members of the class should mount and determine. Such 

 mounts may be made in 2 per cent, acetic acid after treating first with a weak alcohol 

 (10 per cent.) to wet the mycelium, so that the acetic acid will cover the specimen 

 mthout air bubbles and without the h\pha: massing together, as happens frequently 



