Probable Fertile Region of Asteroxylon mackiei K. and L.
Asteroxylon mackiei was first described from the Rhynie Chert by Kidston and Lang1, but the nature of its reproductive region has remained uncertain, since the peculiar leafless axes and small pear-shaped sporangia, which they provisionally assigned to the plant, have never been found connected to its leafy stems.
Earth-Science Reviews - Elsevier Publishing Company, Amsterdam - Printed in The Netherlands C U R R E N T TREN DS IN PALEOBOTANY
The. remarkable growth of paleobotany within recent years is revealed in the exparLded body of literature and by the increase in number of languages in which it is written. New techniques are involved in the use of cuticles and the electron microscope. Precambrian rocks, once regarded as essentially without fossils, have been found to contain a variety of micro-organisms, and compounds believed to be decompos.ition products of chlorophyll have been identified in rocks three billion years old. Some new ideas have developed concerning the morphology and relationships of some of the very old vascular plants. The original reconstruction of Psilophyton embodied more than one plant, and Asteroxylon now appears to be a lycopod. ]'he Hyeniales and Pseudosporochnus belong to the Cladoxylales. Archaeopteris and Callixylon are the foliage and woody trunks of the same plant which has been designated a "progymnosperm". Seeds now appear to have been recognized in the Upper Devonian, and a considerable number of primitive seeds have lately been found in the Lower Carboniferous calciferous sandstone. Decreased coal mining has curtailed the supply of Carboniferous compressions. In North America outstanding progress has been made in the study of petrified plants in coal balls. Studies of the Glossopteris flora have been extended into Antarctica. Continental drift seems to be the only hypothesis that satisfactorily explains the position of the fragments of ancient Gondwanaland at the present time. Reinvestigations of the inflorescences of Cycadeoidea have shown that the structure of the staminate disc was originally misinterpreted. It is a complex synangium that encircles the gynoecium, rather than being a whorl of pinnate stamens. The occurrence of angiosperm leaves in the Lower Cretaceous of Greenland is questioned. Some investigators now believe that angiosperms originated at high altitudes in the tropics during, the Permian Period. Others would derive them from the Glossopteridae during the same period. Fruits and seeds have proved quite usefid in accurate determination of Tertiary angiosperms. Petrified woods create special problems in identification and nomenclature.
Suitability and water quality criteria of an open drainage municipal sewage water at Coimbatore, used for irrigation.
Sanganur canal is the major open drainage system which has intricate linkage with storm water supply, domestic sewage and industrial effluent disposal. Water samples from various stations were collected and analysed for physicochemical parameters to assess the water quality of the Sanganur canal system. The study revealed that physicochemical parameters like pH, EC, TDS, DO, BOD, COD exceeded the permissible limit, clearly indicating the need of proper treatment of waste water before discharge into the Noyyal river.