I2O 



BACTERIA IN RELATION TO PLANT DISEASES. 



I 



at the left : Xylol, second xylol, xylol one-third absolute alcohol two-thirds, 95 per 

 cent alcohol, 75 per cent alcohol, 55 per cent alcohol, 40 per cent alcohol, carbol- 

 fuchsin, 40 per cent alcohol, second 40 per cent alcohol, 55 per cent alcohol, 65 per 

 cent alcohol, 75 per cent alcohol, 95 per cent alcohol, absolute alcohol, second 

 absolute alcohol, xylol, second xylol. From this last jar the material is mounted 

 in balsam. Turpentine may be substituted for xylol in jars i and 2. After the 

 paraffin is fully removed, the slides are passed rapidly from jar to jar (a minute or two 



in each being generally 

 sufficient) until the stain 

 is reached. After remain- 

 ing in the stain the proper 

 length of time (usually 

 three to ten minutes, but 

 sometimes much longer) 

 the slides usually are 

 allowed to remain in the 

 40 per cent alcohols for a 

 number of minutes, with 

 frequent inspection. When 

 they appear to be properly 

 bleached (rather pale) they 

 are passed rapidly through 

 the remaining jars until 

 they reach the xylol, in 

 which they may remain 

 for some time without 

 injury, if they can not be 

 mounted immediately, but 

 they must not be allowed 

 to stand for any great 

 length of time in any of 

 the alcohols. The secret 

 of success lies in obtain- 

 ing just the proper amount 

 of differentiation in the 

 40 per cent alcohol and in 

 not losing any of this later 

 on. To retain the stain it 



Fig. 108* 



is necessary sometimes to omit some of the graded alcohols. 



The time required for properly staining sections varies from one or two minutes 

 to a half day or more, according to the subject and the stain employed. No general 

 rule applicable to all cases can be given. When the material is selected for embed- 

 ding, its serial number, with a full description, is entered in the record book (fig. 112). 



*Fic. 108. One of a series of drawers divided into small compartments for holding infiltrated, 

 embedded material, cut and uncut. 



