Homoeologous chromosome pairing: frequency differences in inbred and intraspecific hybrid polyploid ferns

The homosporous fern Ceratopteris thalictroides (Parkeriaceae) has evolved a polyploid genetic system that serves to store and release genetic variability in spite of self-fertilization and Mendelian homozygosity. This is demonstrated by the segregation of a gametophyte mutant within two inbred tetraploid lines and in their intraspecific hybrid. The segregation behavior can be explained by a model involving a duplicated locus and regular homoeologous chromosome pairing. Homoeologous pairing occurs at low levels in the inbred lines and at a high level in the hybrid, indicating intraspecific differences in chromosome pairing affinities.     

Epidermal patterns of the lemma in some fossil and living grasses and their phylogenetic significance

Morphological study of fossil grass anthoecia of Berriochloa and Nassella collected from Miocene-Pliocene strata in Kansas has revealed well-preserved epidermal structure. This seems to be the first micromorphological information known from fossil grass floral bracts. The epidermal pattern on the lemma in the fossils and their living counterparts are evidence in support of the view that the North American species of Stipa of the section Hesperostipa Elias and species of Piptochaetium have a common ancestry in Berriochloa, and that species of both taxa have been distinct from species of the Nassella, Oryzopsis, and other Stipa since at least the Miocene or Pliocene.     

Residential natural gas consumption: evidence that conservation efforts to date have failed

A new short-term natural gas consumption model is developed, tested against American Gas Association sales data, and applied to the question of the effectiveness of conservation efforts. The results indicate that unit residential gas-heating sales per heating degree-day have remained constant in four major gas-consuming regions during the period 1974 to 1976 and that heating sales have not been affected by the recent sharp changes in price.