1928] Wexelsen: Chromosome Numheis and Morphology in Trifolium 359 



species." On page 92 it is stated, "The diploid number of chromo- 

 somes is sixteen." Figure 62& on tlie same page shows, however, 

 a heterotypic metaphase with 16 bodies, and figure 62cZ a homotypic 

 metapha.se with 16 bodies. From these figures the conclusion must 

 be drawn that the forms investigated by Erith had 32 and not 16 

 as the diploid number. I found the somatic number to be 32 in two 

 varieties of this species. In T. montamim, Bleier found 9 bivalents 

 at first metaphase; the count was not certain and as Karpechenko 

 found the diploid number in montamim to be 16, it is probable that 

 there is no species of Trifolium with 18 as the diploid number. There 

 is now established the following series of haploid chromosome numbers 

 in forty-three species of Trifolium : 



Haploid uuniber of chromosomes.-.- 7 8 14 16 24 about 48 about 130 

 Number of species 11 23 1 3 2 2 1 



The basic numbers of this series are 7 and 8. The 7-series consists 

 of single, double, and possibly higher multiple numbers; the 8-series 

 of single, double, triple, and probably higher multiples. This is the 

 terminology suggested by Belling (1927) ; the term single is used for 

 the species with the basic number, and double and triple for species 

 with two and three times this number, corresponding to the old terms 

 tetraploid and hexaploid. As for the relation between chromosome 

 numbers and the systematic classification of species, Karpechenko 

 (1925) states: "Hence it is evident that in the process of divergence 

 of species of clover certain chromosome changes, undiscerned by 

 observation, have greater significance, whereas the number of chromo- 

 somes plays a subordinate role." The species studied by the writer 

 give evidence in the same direction. Widely different species, such 

 as Trifolium, variegahmn and T. refiexum have the same number of 

 chromosomes, while in one group are found species with 16 and 14 

 chromosomes. Among the American species studied there is no repre- 

 sentative of the 7-series. These species form a regular multiple series, 

 8-16-24. 



Variations in Chromosome Size in the Genus 



The chromosomes in Trifolium are in general small. There is, 

 however, a very large range of variation in length from about l/x in 

 T. vanegatum (fig. Id) to 4/^ in T. refiexum (fig. Ih). There is a 

 still greater difference in total chromosome volume, as illustrated by 

 the complexes of T. variegaUim (fig. If?) and T. dicJiotomitm (fig. 1A-). 



