2O2 



BOTANICAL MICROTECHNIQUE. 



corrosive sublimate well adapted for fixing (cf. 310); and 

 a concentrated alcoholic picric acid solution often does, 

 well. 



According to my own most recent experiments, a saturated 

 solution of picric acid and corrosive sublimate in absolute 

 alcohol seems to be best for fixing chromatophores. I allow 

 it to act about 24 hours on the objects to be fixed and wash 

 it out with running water. The use of an iodine solution 

 for the removal of the sublimate seems unnecessary here,, 

 as I have seen none of the well-known sublimate needles in 

 my preparations. 



Krasser (II, 4) recommends the use of a \% alcoholic so- 

 lution of salicylic aldehyde for fixing chromatophores. He 

 lets it act for 24 to 48 hours on small pieces of tissue. After 

 hardening in alcohol, the sections may be mounted in gly- 

 cerine, glycerine-gelatine, or balsam. If in the latter, the 

 clearing in clove-oil must be made as brief as possible. 



352. Schimper used haematoxylin and gentian violet for 

 staining chromatophores; but I have found iodine green, 

 fuchsin, and acid fuchsin better (cf. Zimmermann V, 6). 



Staining with acid fuchsin is best accomplished by one of 

 the three methods described in 345 to 347. It is easy to 

 make clearly visible the relatively small leucoplasts on each 

 starch-grain in the outer layers of a ripe potato, by the aid 



of method B (cf. Fig. 38, /). 



353- Iodine green is used in 

 concentrated aqueous solution 

 and is either allowed to act 

 for only a short time (-J- to a 

 few minutes) on microtome 

 sections, which are then 

 washed with water and exam- 

 ined in glycerine ; or it is al- 



FIG. 38. Cell-contents from a parenchyma- lowed tO act longer and the 

 cell of a tuber of Solatium tuberosunt, but . . " . j . 



a few layers removed from the cork. After SCCtlOllS are then placed in a 

 fixing with sublimate-alcohol and staining . . , . . 



with acid fuchsin (Method B). /, leuco- solution prepared by mixing 



plasts ; s. starch-grains ; 2, nucleus ; k, 



crystalloid. two parts of common ammo- 



nia with 98 parts of water. In this the sections were left 



I .... 



