HAPLOIDS 



143 



for several years. This plant resembles, in all essential 

 respects, the normal plant, except that it produces a very- 

 small number of haploid pollen grains. These pollen 



Fig. 84. 



A haploid plant of Datura. (After Blakeslee, in Journal 

 of Heredity.) 



grains are the ones that have received one set of chro- 

 mosomes after a rather devastating attempt to pass 

 through the maturation stages. 



Two haploid tobacco plants have been reported by 

 Clausen and Mann (1924) that appeared in a cross be- 

 tween Nicotiana Tabacum and N. sylvestris. Each had 24 



