Satellited chromosomes,systematics and phylogeny inTaraxacum (Asteraceae)

A survey is made of the occurrence, nature and frequency of satellited chromosomes in the agamospermous genusTaraxacum. Species belonging to the 10 sections thought to be most primitive in the genus lack satellited chromosomes. In most other sections, a characteristic satellited chromosome is seen with a large euchromatic region distal to the presumed nucleolar oraniser region (NOR). In sections of a precursor type, there is always one chromosome of this Taraxacum type per haploid genome. In sections thought to be of an advanced type the number of such satellited chromosomes is very unstable, sometimes even within the same tissue. In sectionHamata, two such satellited chromosomes are invariably found in triploids. This finding strongly supports the integrity of this section, suggests that the species of the section are monophyletic, and have evolved from a single ancestor subsequent to the occurrence of obligate agamospermy. In three sections of the genus, satellited chromosomes of the conventional type with a very small distal euchromatic region distal to the NOR are reported for the first time in the genus.     

Glossopteridae, Angiospermidae and the evidence for angiosperm origin

The reproductive units of the Glossopteridae are unisexual gonophylls, some with the potential for direct conversion into angiosperm flowers. Compound fructifications in both major taxa may be anthostrobili or the newly defined anthofasciculi. The enclosure of ovules in the angiosperm manner, but with extrorse orientation, places the beginning of angiospermy in the Permian. A few angiosperm gynoecia are extrorse. The presence of the leaf + branch berberoid unit is traced throughout the plant and accounts for the presence of protostelic bundles in the ventral traces and other parts of the flower. This evidence invalidates the carpel theory, but supports the gonophyll theory. The extensive evidence for relationship from reproductive organs is supported by leaf and petal venation patterns forming a continuous series linking the two taxa.