SPERMATOPHYTES— ANGIOSPERMS 



359 



stamens into pieces before fixing, since they are easily penetrated and 

 infiltrated; in later stages the stamens 77iust not be cut into pieces, 

 since the pollen grains and even the pollen mother-cells are easily 

 washed out. 



The problem of fixing spore mother-cells has received much atten- 

 tion. In fixing mother-cells and the two mitoses by which spores are 



Fig. 127. — Lilium marlagon: reduction of chromosomes in the microspore mother-cells; A, 

 bird's-eye view of metaphase showing 12 pairs of chromosomes; B, one chromosome of each pair is 

 starting for one pole and the other for the opposite pole; C, anaphase, each of the 12 chromosomes 

 starting for the pole in B is seen to be made up of 2 chromosomes, so that 24 chromosomes are 

 going to each pole; D, each nucleus of this two-cell stage contains 24 chromosomes. E, the 24 

 chromosomes of each nucleus of D are being distributed, 12 to each pole, so that each nucleus of F 

 contains 12 chromosomes; the 4 cells of F are young microspores. X530. From Chamberlain's 

 Elements of Plant Science (McGraw-Hill Book Co., New York). 



formed, investigators have used almost exclusively the chromo-osmo- 

 acetic acid solutions of Flemming, some preferring the weaker solution 

 and some the stronger. These solutions were used in nearly all of the 

 work done under Strasburger at the Bonn (Germany) school. 



