244 THE USE OF THE MICROSCOPE 



Test an {iiit.her of each bud l)y squeezing it. out in a, 

 drop of iron-acetocarmine, covering, and examining. Clean 

 and polish a slide and put anthers or cut anthers from tested 

 buds in a line across the sUde an inch from one end. Large 

 anthers, like those of Lilium, should be split lengthwise, 

 and dried in blotting paper, after cutting them across. 

 Too much material should not be used. (If the liquid from 

 the sap-filled cells of the anther walls, and of the connective 

 between the anther loculi, gets into contact with any pollen 

 mother cells before the fixative, such cells are instantly 

 spoiled.) Another clean slide is then held crosswise, and 

 with one rapid slanting or curving sweep, the anthers are 

 pressed out, leaving trails of pollen mother cells across the 

 blank center of the lower slide. This slide (or the other 

 slide, too, if necessary) is then without any delay, inverted 

 in the fixative. The fixative is put in a flat, covered dish, 

 with two thick blank microscope slides placed to support 

 the ends of the inverted slides. The writer uses circular 

 dishes holding three slides, which are well covered by 50 

 cubic centimeters of fixative. The following fixative 

 (resembling one used by S. Nawaschin) has proved satis- 

 factory for demonstrating chromomeres. 



Solution A 



Chromic acid crystals 5 grams 



Glacial acetic acid 50 cubic centimeters 



Distilled water 320 cubic centimeters 



Solution B 



Commercial formalin 200 cubic centimeters 



Distilled water 175 cubic centimeters 



(For metaphase preparations, solution B may be made of 100 cubic 

 centimeters of formalin, and 275 cubic centimeters of water.) 



To prepare the fixative, 25 cubic centimeters of solution 

 A are mixed with 25 cubic centimeters of solution B, and 

 used at once; 3 hours seems sufficient for fixing, but 

 12 hours in the fixative does little apparent injury. 

 Slides are transferred from the fixing reagent to a dish 

 containing a half per cent solution of chromic acid. Here 



