320 



REAGENTS AND PROCESSES 



the solution. By placing the dung of different kinds of animals 

 in a moist chamber, as, for instance, in dishes floating on water 

 and covered with a bell-jar, characteristic fungi will after a time 

 appear on it. 



Single spore cultures of Mucor may be obtained in the following 

 manner: Glass slides are thoroughly cleaned and sterilized by 

 baking. By means of sterilized forceps a single sporangium of 

 Mucor is picked from a spontaneous growth of this fungus on 

 horse-dung or stale bread kept in a moist chamber. The sporan- 

 gium is placed in a sterihzed decoction of horse-dung con- 

 tained in a sterilized watch-glass, which may be placed on an 

 inverted tumbler in a plate of water and then covered with a bell- 

 jar which should dip into the water and form a germ-proof moist 

 chamber. After a few hours the sporangium will have burst 

 open and the spores, which are now distributed through the decoc- 

 tion, will have swollen to several times their original diameter, 

 and can all the more readily be discerned in subsequent manipu- 

 lations. A needle which has been disinfected by heating in a 

 flame is now dipped into the decoction and the point of it drawn 

 along the surface of a glass slide which has been cleaned and 

 sterilized as above directed. By this process the decoction which 

 has adhered to the needle is drawn out in the form of a narrow 

 streak, and if several spores of Mucor are present, they will be 

 separated from each other. A single spore may be located with 

 a medium power of the compound microscope, and all other 

 spores present in the streak may be wiped off with a cloth which 

 has been sterilized by heat. Then a drop of the decoction of 

 sterilized horse-dung should be added to the small amount con- 

 taining the spore on the slide. The slide should be placed in a 

 moist chamber where the spore will soon give rise to a mycelium 

 visible to the naked eye, and from the mycelium numerous spo- 

 rangia will be produced after a time. The slide may be taken 

 from the moist chamber from time to time and the stages in the 

 development of the fungus examined, but as much care as possi- 

 ble should be taken to prevent the contamination of the culture. 



Knop's nutrient solution, which is particularly good for the 



