Cytology of Sphagneticola and Wollastonia, two genera in Heliantheae, Asteraceae.
Chromosome number and chromosome morphology in Sphagneticola O. Hoffm. and Wollastonia DC. ex Decne., two small genera in Ecliptinae, Heliantheae, Asteraceae, were investigated. The results showed that the karyotype formula were followed as: Sphagneticola calendulacea (L.) Pruski, 2n=50=18m+30sm+2st, S. trilobata (L.) Pruski, 2n=56=24m+28sm+4st, Wollastonia biflora (L.) DC, 2n=30=24m+4sm+2st, and W. montana (Blume) DC., 2n=74=37m+31sm+6st. Based on the results, together with chromosomal data previously reported in Sphagneticola, we postulate the basic chromosome numbers of this genus as x=14 and x=25, rather than x=15. The three species native to the New World tropics in the genus, namely S. brachycarpa (Baker) Pruski, S. gracilis (Richard) Pruski and S. trilobata, may be based on x=14, with S. gracilis being diploid (2n=2x=28), and both S. brachycarpa and S. trilobata tetraploid (2n=4x=56); the only Asian species, S. calendulacea, may be diploid (2n=2x=50) based on x=25. The systematic implication of this chromosome number pattern is worthy of a further study. Chromosomal data do not support the placement of W. montana (x=37) in the genus Wollastonia (x=15).