Methods for absolute diatom frequency analysis and combined diatom and pollen analysis in sediments

Earlier methods for absolute diatom frequency analysis were timeconsuming. In pollen analysis the use of indicator pollen and spores is well established. This method has been tested for absolute diatom analysis and proved to simplify the work. A detailed preparation procedure is given. A method for combined pollen and diatom analysis has been worked out to check the diatom production curves in sediments where the deposition rates can not be measured by ¹⁴C–dates or yearly laminated sediments. Diatom frequencies are here compared with synchronous terrestrial pollen frequencies. This gives an independent picture of changes in diatom productivity.     

On the highest units in the system of plant communities

It is evident that some higher syntaxonomic unit above the classes is needed. The “circle of vegetation”, proposed byBraun-Blanquet is a geographical, not a synecological unit; the “formation”, recommended recently byPassarge, is based on physiognomy and therefore inconsistent with the principles of lower entities. The “division” proposed recently by Jakucs seems to be identical with the “type of vegetation”, published already 11 years ago by the present author.     

THE TUBERCULOUS DISEASES Originating from Different Species of Acid-Fast Bacilli

Disease due to the typical human type tubercle bacillus is rapidly diminishing as a result of public health measures and specific chemotherapy. Lesions in man resulting from other kinds of acid-fast bacilli are now being recognized in increasing numbers. Some of these bacilli had been seen before but were confused with typical M. hominis, others were considered to be harmless saprophytes, while others could not be found with the methods used. Special culture media, different conditions for cultivation, new physical, chemical and biological tests, and inoculation into a variety of animal hosts are now available. With their use more than a dozen different strains of human type tubercle bacilli, and more than a score of other species of acid-fast bacilli may now be distinguished. A simple chemical test readily separates the human type tubercle bacilli from all other kinds of acid-fast bacilli. The differentiation of the different human and animal pathogenic acid-fast bacilli from the avirulent saprophytes and other harmless mycobacteria presents great difficulties, but methods are becoming available which usually make this possible. Since the distinction may be of great therapeutic and epidemiologic importance, the effort should be made.     

An Improved Hematoxylin-Eosin Stain for Sections of Marrow Units

The procedure recommended is: Fix “marrow units” (small functional structures of bone marrow) in 10% formol-saline solution for 1-2 hours and dehydrate in 80% alcohol, 95% alcohol and acetone 30 minutes each. Place in fresh 50° and 53°C. paraffin for 30 minutes each. Embed in fresh 53°C. paraffin. Serially section at 5μ thickness and mount with Schleicher's floating solution. Allow to dry for 1 hour in an oven and deparaffinize by passing through xylene I and II, absolute alcohol I and II, and 95% alcohol. Rinse in fresh distilled water and place in dilute Harris' hematoxylin (stock solution 50 ml., distilled water 200 ml.) for 2 to 3 minutes. Rinse well in distilled water and check staining under the microscope. Dip in acid-alcohol 5 times (1 dip to equal about 1 second). Rinse well in weak (0.02%) ammonia water and distilled water. Dip in 2% aqueous phosphotungstic acid about 3 to 5 times (equal to 3-5 seconds). Rinse in fresh distilled water and place in weak ammonia water for 1 minute. Rinse in fresh distilled water I and II. Place in 80% alcohol for 5 minutes and check under the microscope for “blueness” and nuclear differentiation. Place in dilute alcoholic eosin (0.5% alcohol-eosin stock solution 10 parts and 95% alcohol 90 parts) for 1 to 2 minutes. Rinse in 80% alcohol and place for 1 minute in 95% alcohol. Check under the microscope for staining quality. Place in absolute alcohol for 1 minute, alcohol-xylene (equal parts), 10 dips, and xylene I and II. Mount. This hematoxylin-eosin staining schedule brings out minute structural detail of bone marrow tissue heretofore not demonstrable.     

THE ACTION OF SODIUM DODECYL SULFATE ON THE CHLOROPHYLL-PROTEIN COMPOUND OF THE SPINACH LEAF

1. Sodium dodecyl sulfate (SDS) attacks the chlorophyll-protein compound modifying its protein properties and absorption spectrum. 2. In the presence of SDS, chlorophyll is quantitatively converted to phaeophytin; i.e., magnesium is removed from the molecule. This reaction, measured spectrophotometrically, proceeds at a rate directly proportional to the hydrogen ion concentration. At constant pH, the rate is proportional to the SDS concentration until a maximum rate is achieved. 3. The chlorophyll or phaeophytin (depending on the pH) remains attached to the protein, since the prosthetic group cannot be separated by ultrafiltration, dialysis, or fractional precipitation. 4. This suggests that the magnesium plays no part in binding chlorophyll to the split protein fragments, but may be concerned in binding the larger units, since the metal becomes extremely labile when the protein is split.     

THE INDUCTION PERIOD IN PHOTOSYNTHESIS

1. Measurements on the photosynthesis of Cabomba caroliniana show an induction period at low and high light intensities and CO₂ concentrations. 2. The equation which describes the data for Cabomba also describes the data obtained by other investigators on different species. The phenomenon is thus shown to be similar in plants representative of three phyla. 3. A derivation of the induction period equation is made from a consideration of the cycle of light and dark processes known to occur in photosynthesis. The equation indicates that light intensity enters as the square, and that the same light reactions are involved as those which affect the stationary state rates. However, a different dark reaction appears to limit photosynthesis during the induction period.