Our study suggests a fungus belonging to Sebacinales group B as the main fungal host of the D. alpinum gametophytes. However, Sebacinales group B fungi occur as well in adjacent Ericaceae plants; therefore, we assume the mycoheterotrophic gametophyte to be epiparasitic on Ericaceae, which would explain the steady association of these plants.

ABSTRACT:The objective of research was to determine the density of juvenile (JW) and mature wood (MW) of selected coniferous species growing in the Czech Republic. The research included the wood of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and European larch (Larix decidua Mill.). The juvenile wood density close to the pith was 410 kg·m -3 for spruce, 391 kg·m -3 for pine and 573 kg·m -3 for larch with 12% water content. Mature wood in the peripheral parts had the higher density in all species -spruce 516 kg·m -3 , pine 552 kg·m -3 and larch 652 kg·m -3 . The highest difference, the difference of 161 kg·m -3 , between juvenile and mature wood was found out in Scots pine. The large difference in the wood density of pine is caused by a considerable difference in the mean ring width of its juvenile and mature wood. Further, it was proved that wood density decreases with the increasing ring width while wood density increases with the increasing proportion of latewood.

As long-lived reptiles, Mojave desert tortoises (Gopherus agassizii, Cooper 1861) are expected to make substantial energetic investments in immune-defense. This species also has many adaptations to living in an arid environment characterized by seasonal extremes in temperature and resource-availability. By housing tortoises at a controlled, constant ambient temperature, we quantified predominantly temperature-independent seasonal fluctuations in innate immune function and circulating leukocytes in a reptile. We found a decrease in bacteriocidal activity of the blood plasma in winter, with reduced function lasting into the spring. Lymphocyte numbers were elevated in fall and winter, while eosinophil numbers increased in summer. Thus, properties of the immune system were up or down-regulated in different directions across the seasons. We found a much higher level of variation of leukocyte profiles among individuals than has previously been reported for other chelonians. Heterophil:lymphocyte ratios (indicative of chronic glucocorticoid levels)were not associated with any measure of immune function, and thus glucocorticoid does not seem to mediate the observed seasonal changes. We propose a new hypothesis to explain seasonal changes in immune function, based on seasonal resource-limitation in the Mojave Desert -including the availability of dietary protein, energy, and opportunities for thermal regulation.

Diploid hybrids have retained their genetic and morphological identites throughout their Central European range, and thus no indications for diploid backcrossing were found. The triploid hybrids have probably originated from backcrossing between a diploid gametophyte of a hybrid (derived from a diplospore) and a haploid gametophyte of a diploid parental species. By repeated crossing events, reticulate evolution patterns arise that are similar to those known for a number of ferns.

A Diphasiastrum taxon being morphologically intermediate between D. alpinum and D. tristachyum is described as D. oellgaardii. During gel isoenzyme analyses, glucose‐6‐phosphate isomerase and esterase turned out to be electrophoretic markers testifying the hybrid origin of D. oellgaardii. In Europe, where three parental species (D. alpinum, D. complanatum and D. tristachym) occur, D. oellgaardii is the third taxon of hybrid origin besides D. issleri and D. zeilleri. Problems of reproductive biology of these taxa are discussed.