Pollen morphology and relationships in the genus Calandrinia H.B.K.

Analysis of a number of morphological characteristics in the herbaceous genus Calandrinia H. B. K. (Portulacaceae) suggest that two natural groups of species exist, one in western North and South America and the Galapagos Islands, another in Australia. The morphology of pollen grains, seeds, and hairs proved most useful in establishing the limits of the subgeneric taxa. The twelve sections created by Reiche for the American species are accepted. One new section is created to accommodate two American species described since the work of Reiche. The sections recognized by von Poellnitz for the Australian representatives of the genus appear, with one exception, to be invalid. The genus probably originated in the early Tertiary. Continental drift may prove to be the best explanation for the present pattern of distribution of the genus.