FORMATION AND GERMINATION OF SPORES. 133 



should be left in for about two miautes; but the 

 best plan is to place a few drops on the cover-glass, 

 until it is completely covered, and then to move it 

 continually backwards and forwards over a gas flame 

 until steam begins to be formed. The liquid, however, 

 must not be allowed to boil, or the preparation will 

 not be clear. 



The cover-glass is then rinsed and examined with 

 the microscope. Now, instead of the bright spots, 

 intensely coloured ones are to be seen, forHhe spores 

 are able to absorb more stain than the vegetative cells, 

 which have already begun to lose their vitality, and as 

 the spores approach maturity always become less 

 readily stained. The difference in colour is, however, 

 not sufiBciently marked ; this can only be attained by 

 means of contrast staining. 



The spores being diflScult to stain, are also difficult 

 to decolourise ; the preparation may therefore be 

 rinsed with dilute acetic acid (5%) until the rodlets 

 appear decolourised; the time this takes varies accord- 

 ing to the intensity of the colouration. It is best to 

 examine the cover-glass, therefore, from time to time 

 with the microscope, so as to see when sufficient de- 

 colourisation has taken place. When the rodlets are 

 colourless, or nearly so, the cover-glass should be 

 immediately rinsed with water. The spores are cer- 

 tainly somewhat lighter, but they are still a deep red. 

 The preparation can now be treated for a few minutes 



