CHROMOSOME NUMBERS IN COMPOSITAE. II. HELENIEAE

Raven , Peter H. (Rancho Santa Ana Botanic Garden, Claremont, Calif.), and Donald W. Kyhos. Chromosome numbers in Compositae. II. Heleniae. Amer. Jour. Bot. 48(9): 842–850. Illus. 1961.—Chromosome counts are now available for 42 of the approximately 55 genera of Compositae, tribe Helenieae, which is predominantly a group of western North America. These chromosome numbers are summarized here at the generic level, and 100 original counts for the tribe are added, including what seem to be the first published reports for the genera Amblyopappus, Baeriopsis, Hulsea, Jaumea, Pericome, Rigiopappus, Trichoptilium, and Venegasia, as well as for many species. The phylogeny of Chaenactis is discussed in the light of published records and 46 original counts, and C. douglasii is shown to include plants in which n = 6, 12, and 18, which differ somewhat morphologically. Helenium has species which have a complete series of aneuploid numbers from n = 13 to n = 17. Chromosome numbers coincide with morphological variability in indicating that Helenieae are a diverse group. More detailed studies of various kinds will be necessary before the genera of Helenieae can be re-aligned effectively, but it is evident that different genera show affinities with various other tribes of the family. Nevertheless, it is thought to be convenient to continue to recognize Helenieae at the tribal level for the present.