The tribe Tigridieae (Iridaceae) is strictly a New World group with centers of diversity in Temperate and Andean South America and Mexico. Generic boundaries, species affiliation, and phylogenetic relationships are problematic and vary considerably from one specialist to another. A phylogenetic hypothesis for 23 species of the tribe Tigridieae (Iridaceae), based on nucleotide sequence variation from the internal transcribed spacers (ITS) of nuclear ribosomal DNA and three intergenic spacers of the cpDNA (psbA-trnH, trnT-trnL, and trnL-trnF), showed the utility of pollen morphology and karyotype to define two subtribes of Tigridieae. Typically, the pollen grains have one aperture in subtribe Cipurinae and two apertures in subtribe Tigridiinae. Similarly, somatic cells have 2n = 14 in Cipurinae and 2n = 28 in Tigridiinae. Pollen morphology and chromosome number remain unknown for some species of Tigridieae. Ainea conzatii and Cardiostigma hintonii are members of Cipurinae, both endemics of Mexico. We used the scanning electron microscope (SEM) and the Feulgen stain technique to observe pollen morphology and mitotic figures on these two taxa. Both species have bisulcate pollen grains and the sporophytic chromosome number is 2n = 28. The results suggest the affiliation of A. conzatii and C. hintonii to Tigridiinae rather than Cipurinae. Finally, the results highlight the integration of morphological and molecular data to estimate phylogenetic relationships.

Key words: Ainea, Cardiostigma, cytology, phylogeny, pollen, Tigridieae