Cytology of Antennaria. I. Normal Species

Abstract

I. A. neglecta and A. plantaginifolia reproduce in the normal sexual manner, and in both spp. meiosis is regular. In both spp. n=14, but there is evidence that the basic number for the genus is 7. In the hybrid A. neglecta [image] plantaginifolia various meiotic irregularities are found, resulting in a varying percentage of sterility, both in the staminate and the pistillate plants. One presumably aposporic embryo sac was found in this hybrid. In A. solitaria, n=14; occasional slight irregularities in meiosis occur.[long dash]II. Seven spp. of Antennaria of the eastern U. S. A., here studied, reproduce partheno-genetically. Microsporogenesis in A. jallax, A. parlinii, and A. canadensis is irregular, while the semiheterotypic division is frequent in A. canadensis. The megaspore mother cell usually develops directly into a diploid embryo sac, the egg cell of which develops partheno-genetically; but an abnormal type of megasporogenesis occasionally occurs, the products of which degenerate. The approximate 2n numbers are: A. fallax, 84; A. parlinii, 84; A. canadensis, 83-86; A. petaloidea, 75-80; A. occidentalis, 75-85; A. neodioica, ca. 52; A. brainerdii, 42. In some spp. taxonomic evidence supports cyto-logical that they have arisen from hybrids between sexual spp. by an increase of the chromosome number.