366 University of California Publications in Agricultural Sciences [Vol. 2 



explain why Karpechenko did not find any satellites in T. prafense 

 and T. incarnatum, in each of which 1 pair of conspicuous satellites 

 was found. Of the species in which no satellites were found, only 

 one, T. hyhridum, has been investigated thoroughly enough to state 

 with certainty that it does not have satellites. 



The existence of satellites was first established by S. G. Nawaschin 

 (1912) in Galtonia. Since that time they have been obser^'ed in many 

 species and genera. The most outstanding works are those of M. 

 Nawaschin (1925, 1926) on the genus Crepis and of Taylor (1924, 

 1925, 1926) on Crepis, Gasteria, Allium, and other genera. In the 

 Leguminosae, satellites have been found in Pisum, Lathyrus, and 

 Vicki (Nawaschin, 1925; Sveshnikova, 1927). 



The satellites in Trifolium are large compared with those observed 

 in most other species. T. fucatum (fig. 1/) seems to have smaller 

 satellites, while T. virescens which is nearly related to fucatum, and 

 perhaps should be regarded as a variety (fig. Ig) of this species, has 

 large satellites. This may be a case of the same nature as that reported 

 by Nawaschin (1926) in Crepis dioscoridis, in which he found strains 

 differing in satellite size. It cannot be stated with certainty that 

 there is a real difference in satellite size in fucatum and virescens. 

 There is some variation in satellite size within the strains and as the 

 chromosomes of fucatum. were much crowded on the plates only a few 

 observations of satellites were made in this species. In virescens, 

 however, many observations were made, but satellites as small as those 

 observed in fucatum were never seen. 



A peculiar feature of these satellites is that they sometimes seem 

 to lie free on the metaphase plate without any visible connection Avith 

 any of the chromosomes, as shown in the metaphase plate of T. 

 pratense (fig. 2a). The free satellites often have a more elongated 

 shape, resembling very much a pair of small chromosomes. Anyone 

 unfamiliar with the material would in such plates count 16 chromo- 

 somes in pratense and 18 in alexandrinum . In these two species the 

 reduction divisions in the pollen mother cells were also studied. In 

 alexandrinum, many plates of the first metaphase .showed 8 bivalents 

 (fig. 4a) and, in agreement with this, 8 chromosomes were found at 

 second metaphase (fig. 46). No trace of satellites was found at these 

 stages. In T. jyratense, both Bleier and Karpechenko found the 

 haploid number to be 7 in the reduction divisions of pollen mother 

 cells. Although only a little pollen mother-cell material of T. pratense 

 was available, several good diakinesis plates showed 7 bivalents 



