Xo.ol3] 



NOTES AND LITERATURE 



work. The further history of the reduction mitoses is not de- 

 scribed, so that the investigation is incomplete in a number of 

 important features. 



The second paper of Rosenberg deals with (',■< i>is virens, one 

 of the Composite, a form remarkable for the small number of 

 chromosomes, which arc 1 six for the sporophyte and three for 

 the irametophyte generation. A further important peculiarity 

 is a difference in the size of the chromosomes which makes it 

 possible to follow the individual elements through succeeding 

 mitoses with some degree of certainty. This is, so far as the 

 reviewer is aware, the first account for plants of such a differ- 

 entiation of chromosomes as has been described for animals by 

 a number of zoologists. 



The nuclei of the sporophvte (somatic) show six small pro- 

 chromosomes in the resting slauv from which are o.-ani/ed dur- 



chromosomes, two very long bent elements, and two chromosomes 

 about midway in length between these extremes. The resting 

 nuclei of the pollen mother-cells have six prochromosomes more 



parallel threads intimately united aUntervals. From this con- 

 dition a thick coiled spirem is organized which clearly shows its 



the period when the six chromosomes, grouped in three pairs, 



