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SAMUEL E. HILL. 



reduced number of chromosomes, and can always be recognized. 

 The material was fixed in Carney's acetic-alcohol-chloroform, and 

 stained with Heidenhain's iron hematoxylin. No counterstain was 

 used. The maturation divisions apparently consume very little 

 time, for metaphase stages were never found in material which 

 was fixed later than five minutes after collection. Since the buds 

 are very small, dissecting out the anthers in this limited time was 

 impracticable, so all of the unopened buds of a raceme were fixed 

 at once. The raceme was then sectioned, usually at 6 micra. The 

 cells at the time of the first maturation division are about 10 

 micra in diameter. It was possible to find cells cut at right angles 

 to the spindle, so that the metaphase chromosomes were disposed 

 in a horizontal plane. Counts were made in all of the species of 

 the Rubella group. Marchal's count of 8 haploid chromosomes 

 for Bursa Viguicri was confirmed, and 8 haploid chromosomes 

 were found in the other three species. In B. grandiflora the 

 diploid count also was made, and found to be 16, but somatic 

 counts were not made for the other species of this group. In the 

 Bursa-pastoris group not all of the species were counted, as sev- 

 eral were unavailable, and in one available species no count was 

 made. Rosenberg's count of 16 haploid chromosomes, 32 diploid 

 chromosomes for B. bursa-pastoris was confirmed, and 16 haploid 

 chromosomes found for B. ocddentalis, B. orientalis, and B. bursa- 

 pastoris apctala. As far as counted, these two groups are as 

 sharply divided on the basis of chromosome numbers as on the 

 results of breeding experiments. 



We may tabulate the chromosome numbers in the genus Bursa 

 as follows : 



