1928] Wexelscn: Chromosome Numbers and Morphology in Trifolium 369 



T. a lexan drin um : 



1 pair of satellited chromosomes. 



1 pair of large, constricted chromosomes. 



3 pairs of medium, constricted chromosomes. 



2 pairs of medium cliromosomes without visible constrictions. 

 1 pair of small, constricted chromosomes. 



The complexes in tlie last two species are similar but alexandrinum has one 

 more pair of medium sized chromosomes. 

 T. hyhridum: 



6 pairs of large chromosomes, at least three pairs with consti-ictious. 



1 pair of very small chromosomes. 



1 pair of small, constricted chromosomes. 



The smallest pair of chromosomes in hyhridum is of the same size 

 as the satellites of pratense, and the plates of hyhridum resemble very 

 much the plates of pratense in which the satellites have no visible 

 connection with the chromosomes. ^ 



In T. repens, Bleier found in the first metaphase of the reduc- 

 tion division 4 small and 10 large bivalents. The somatic plates 

 studied also indicate that there is one group of small and one of large 

 chromosomes, but it is very difficult to get 32 chromosomes, all lying 

 flat on the plate, so that nothing can be said with certainty as to the 

 number of chromosomes in each group. It may be of interest to note 

 that in the two nearly related species, hyhridum and repens, we find 

 in the former 2 pairs of small chromosomes and in the latter prob- 

 ably 4 pairs. In one plate of repens (fig. 3e) 1 pair of satellited 

 chromosomes was seen, so it is probable that repens has satellited 

 chromosomes. As hyhridum has no satellites this would mean that 

 repens has not simply twice the complex of hyhridium.. 



Outstanding in their chromosome morphology are also T. minus 

 and T. reflexmn. It is interesting that the double species, T. minus 

 (32 diploid), has probably 3 pairs of satellited chromosomes (fig. 2g) 

 while no single species has been found with more than one pair of 

 satellites. 



T. reflexum (fig. 1/) exhibits a chromosome complex different from 

 all other investigated species, with 5 pairs of large constricted 

 chromosomes and 3 pairs of smaller chromosomes. 



