Saharatheca lobata n. gen. and sp.: a new medullosan (seed fern) pollen organ from the Middle Pennsylvanian of Illinois

Several specimens of a pollen organ containing Monoletes pollen occur in a single coal ball collected from the Herrin No. 6 Coal at the Sahara Coal Company Mine in southern Illinois. Specimens are 3–4 cm long, up to 1 cm wide, and are either bilobed or trilobed; 5–7 pollen sacs are arranged along each side of a discontinuously sclerified ground tissue plate extending into each lobe. The vascular supply from the peduncle breaks up by repeated dichotomies and one bundle descends along the outer side of each pollen sac. The mode of dehiscence and the structure of the tip of the organ remain unknown. Each lobe (and contained sporangia) is hypothesized to be derived from an ancestral fertile frond segment bearing pendulous sporangia.

Studies on the physiology and propagation of the ostrich fern, Matteuccia struthiopteris

SynopsisThe effect of photosynthetic photon flux density (PPFD), water, temperature and nutrition on frond emergence, vegetative frond production, fertile frond production, vegetative propagation and dormancy is examined. Ostrich fern plants will not break winter dormancy until they have received a minimum amount of cold exposure below a base temperature which is above 5.8°C and may be as high as 20°C. After the plants have received their chilling requirement, vegetative frond emergence does not occur until temperatures at or above ca. 9.3°C are reached. Percent germination and rate of emergence increases up to ca. 24°C. Photosynthetic photon flux density, water availability and mineral nutrition can affect both vegetative and fertile frond production but water availability appears to be the most critical. A mild water stress of −0.15MPa can have significant effects on water status and gas exchange in fronds. Sporophyte plants for field production have been produced vegetatively from detached meristems occurring naturally on the rhizomes, and through fertilization of axenic gametophytes.

Aspects of the Biology of Laminaria Hyperborea III. Survival and Growth of Gametophytes

The lower limit of the Laminaria hyperborea (Gunn.) Foslie zone is probably not always determined only by lack of sufficient light, even when a suitable substratum is present (Kain, 1962). It also appears that the establishment stage is critical although growth conditions deteriorate with depth (Kain, 1963). It therefore seemed desirable to determine exactly what the light requirements of the various different early stages were, and relate these to what could be found out about the light penetration in the natural habitat. The effect of temperature on these stages is also of interest, in relation to the seasonal cycle as well as to the geographical distribution of the species. In this study two different techniques were used: culturing the gametophytes on cover-slips and also studying changes in oxygen concentration as measured by the Winkler method.The gametophytes of the different members of the Laminariales show a similar general course of development. A zoospore from a fertile frond of a Laminaria plant loses its motility, rounds off, swells and produces a tube with another sphere at the end into which all the cell contents pass (Killian, 1911). This process can be carried through in the dark but further development depends on light (Schreiber, 1930). In this genus the gametophytes are dioecious (Sauvageau, 1918; Williams, 1921) and equal numbers of male and female plants are produced (Schreiber, 1930). The female gametophyte may become fertile before dividing further (Sauvageau, 1918), resulting in a single egg, or may form a luxuriant filamentous structure which may produce many oogonia over a period of time (Ikari, 1921; Myers, 1925; Schreiber, 1930).