458 



NATURE STUDY AND LIFE 



grows. P'riiit juice as it comes from preserves, — as clear 

 and colorless as possible, — diluted one-half and filtered 

 or strained through fine cheese cloth, makes an ideal 

 medium. Fill the vial or glass half full and sprinkle a 

 little dust from the schoolroom over the surface. Cover 

 and set aside to observe from day to day. Three such 

 cultures should be made, one of which should be kept in 

 a dark place, one in a room where direct sunlight does 



not fall upon it, and the 

 third should be kept in 

 the sunshine as much 

 of the time as possible. 

 It would be better if 

 each of the pupils had 

 a vial and one-third 

 kept theirs in the dark, 

 another third, on their 

 desks, in the shade, and 

 the other third, in the 

 sunshine. Then let 

 them compare notes 

 during the nature-study 

 period and decide under 

 what conditions moulds 

 grow best. Let them 

 vary the e.\perimcnt to see if they can discover conditions 

 under which moulds are unable to grow at all. Experi- 

 ment by leaving the dust in the bright sunshine for one, 

 two, or three days before planting it in the fruit juice. 

 It should be kept in a dry vial stoppered with a plug of 

 cotton batting. But before we can go further with this 



Fig. 1S9. ^Ictiii.u Gariii.:ns 

 The liquid culture is seen at the light. The 

 others show arrangement for solid cultures. A 

 little water is put in to keep tlie air moist, and 

 the material is supported on a piece of glass 



