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The advent of reproduction by seeds was one of the most essential evolutionary steps in plant history: the vast majority of living plants are seed plants (spermatophytes). The seed habit includes the following set of defining characteristics: (1) heterospory, (2) occurrence of a single megaspore that germinates within an indehiscent megasporangium (nucellus) retained on the sporophyte, (3) enclosure of the megasporangium in an integument, and (4) capture of pollen before seed dispersal. Contrasting hypotheses about the single / multiple, saltational / gradual origin of the seed habit, and identification of the closest relatives of seed plants (aneurophytalean or archaeopteridalean progymnosperms) are still matters of considerable debate. Early seeds did not possess the whole set of characters that define modern seeds. They lacked a true micropyle and an entire integument, and none has yet been discovered containing an embryo. Hence they are called preovules.

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Misten Bog has through time received homogeneous pollen rain dominated successively by Fagus, Quercus and Picea. Based on the limits separating six pollen zones across nine cores, we show that the areas of major peat production have moved with time from one side of the bog to the other. The reduction of thickness of peat was strongly dependant on the proximity of peat cutting area since the 12th Century. Before the cutting, an Alnus wood that encircled the bog regressed during the Vandal Minimum (500-800 AD) and never recovered. During this age interval, testate amoebae indicate a drier period on the peat bog. From the 12th to the 14th Centuries, there was a slight increase of non arboreal pollens linked to farming. From the 14th to the 16th Centuries testate amoebae indicate again a drier period on the peat bog but whether this is linked to climate change or human pressure is unclear. From the 16th Century onwards, Sphagnum sect. Cuspidata almost disappeared but Sphagnum imbricatum persisted until the 19th Century. Pollens linked to farming culminated again during the early part of the 19th Century. High concentration of Si, Ti and N are probably linked to the increasing farming in the neighborhood as well as to industrial mining processes in the region and might have influenced these changes on the peat bog. The theory of cyclical hollow/hummock succession versus rather stationary hummocks is discussed. [ABSTRACT FROM AUTHOR]

A number of motored auger holes have been drilled in 2002 and 2006 in four sand-clay deposits preserved in dissolution pockets within the Dinantian limestones of the watershed north of the Vesdre valley. These deposits of unknown age are currently classified as (Tertiary) SBL in the new geological map of Wallonia. We present detailed lithostratigraphic logs of the deposits and describe the results of sedimentological and mineralogical analyses. In particular, K-Ar dating of neoformed Mn oxides found at the base of one augerhole at Rechain yielded ages ranging from Cenomanian to Santonian, allowing us to place the Rechain and Andrimont deposits within the early Late Cretaceous. This is fully consistent with their topographic location very close beneath the trace of the pre-Cretaceous erosion surface and makes them the westernmost remains of the Hergenrath Member of the Late Cretaceous Aachen Formation. To the west, the Magnée deposit is more "typical SBL', probably corresponding to the Late Neogene filling of a dissolution pocket by reworked weathering products of the local Cretaceous cover. [ABSTRACT FROM AUTHOR]