Chromosome Numbers in Senecio (Compositae). I

Chromosome numbers are reported for 65 collections representing 30 species of Senecio. The following chromosome numbers are reported for the first time: S. antennariifolius, n = 23; S. bolanderi, n = 23; S. capitatus, n = 20; S. elmeri, n = 20; S. erucifolius, n = 20; S. flettii, n = 20; S. litvinovii, n = 20; S. megacephalus, n = 20; S. pseudaureus, n = 20 and n = 40; S. robbinsii, n = 23; S. rupester, n = 10; S. uniflorus, n = 20; and S. websteri, n = 20. A relatively high incidence of intraspecific polyploidy is reported with six Northwest species exhibiting the phenomenon.