292 MTJCOR. 



422. Germination of Gonidium. To follow the germination 

 of the gonidia, make hanging-drop cultures in a moist-chamber 

 slide ( 18). Boil some French plums or prunes in water to make 

 a dilute decoction of the juice (five prunes to 100 c.c. of decoction) ; 

 boil the juice in order to sterilise it and to prevent the growth of 

 other Fungi, and place a drop of it on a cover-glass. Moisten 

 a needle with the boiled juice, touch a ripe gonidangium with the 

 needle-point, and dip the latter in the drop on the cover, the object 

 being to place in the drop as few gonidia as possible. Invert the 

 cover and watch the germination : the gonidium puts out a hypha, 

 which branches repeatedly, the branches spreading out radially in 

 all directions. 



In these culture experiments, all the apparatus used must be 

 sterilised as thoroughly as possible, the prune juice or other nutrient 

 medium by boiling, the needle by heating in a spirit-lamp or Bunsen 

 flame and allowing to cool, the moist-chamber slide and cover by 

 placing them in boiling water for a short time. 



Instead of prune juice, Pasteur's fluid ( 410), or a decoction of 

 horse dung, may be used for Mucor. Cultures should also be made 

 in agar or gelatine, mixed with prune juice and with cane sugar and 

 placed in Petri dishes (shallow glass dishes with slightly wider 

 glass covers fitting over them) in each case all the utensils and 

 nutrient media must be sterilised by exposing them to a tempera- 

 ture of 100 C. for at least half an hour, or to a higher temperature 

 for a shorter time. 



423. The "Torula" or Yeast-condition of Mucor can lo in- 

 duced by making a culture of gonidia (or of a portion of mycelium) 

 submerged in cane-sugar solution or in Pasteur's solution to which 

 sugar has been added. The hyphae become divided up by cross- 

 walls into cells (gemmae) which proceed to undergo budding in 

 the same way as Yeast cells, and like Yeast set up alcoholic 

 fermentation, alcohol and carbon dioxide being produced by 

 decomposition of sugar. On being exposed to the air again, by 

 filtering off the turbid liquid and keeping the residue under ordinary 

 culture, the plant may pass into its normal condition and produce 

 gonidangia as usual. 



424. Sexual Reproduction in Sporodinia. It is 



often difficult to obtain material showing the sexual 

 organs of Mucor, nor is there any method for inducing 

 their formation by cultivating the plant on special culture 

 media, or at altered temperatures. Sometimes one does 

 succeed by making several cultures and mixing the 

 mycelia, for instance by sowing on one piece of bread 

 spores from several isolated cultures. 



