Spermatophytes Angiosperms 



271 



of 2 parts of absolute alcohol and 1 part glacial acetic acid. They 

 allowed the fixing agent to act 15 to 20 minutes, then washed in 

 absolute alcohol, and imbedded by the usual methods. This propor- 

 tion of acetic acid seems entirely too large for any accurate work 

 with chromatin, and we doubt 

 whether the structure of the 

 cytoplasm is normal when so 

 much acetic acid is used. 



The entire pollen mother 

 cell may be stained and mounted 

 without sectioning. Two de- 

 scriptions of technic appeared 

 in 1912, one by Mann 1 and the 

 other by Pickett. 2 Mann re- 

 moves the pollen mother cells 

 before fixing and staining; 

 Pickett fixes and stains the 

 anther in toto and teases out 

 the pollen mother cells just 

 before mounting. 



In Mann's method, the 

 anther is placed in a drop of 

 water and the tip is cut off; a 

 gentle tapping with a needle 

 will then cause the pollen mother 

 cells to float out into the drop. 

 Fix in Bouin's fluid, 4 to 8 hours, 

 wash in 50 per cent alcohol 

 until no color remains, and then 

 stain in iron-haematoxylin. At 

 this stage we should put the material into 10 per cent glycerin and 

 follow the Venetian turpentine method. 



Pickett fixed entire anthers in chromo-acetic acid for 30 hours, 

 washed in water for 24 hours, and then passed up to 80 per cent 



1 Mann, Albert, "The Preparation of Unbroken Pollen Mother Cells and Other 

 Cells for Studies in Mitosis," Science, 36: 151-153, 1912. 



2 Pickett, F. L., "Preparation of Whole Pollen Mother Cells," Science, 36: 479-480, 

 1912. 



FIG. 95. Erythronium americanum: 

 photomicrograph of mature pollen grains; 

 the one at the top, which is cut longitudin- 

 ally, shows both the tube nucleus and the 

 conspicuous generative cell; the other is 

 cut transversely and shows the generative 

 cell, but not the tube nucleus; stained in 

 safranin and gentian-violet; from a prep- 

 aration by Dr. Lula Pace; Cramer con- 

 trast plate; 4 mm. objective; ocular X4; 

 yellowish-green filter; bellows, 85 cm.; 

 exposure, 3 minutes. X615. 



