G. Fekete szerk.: Studia Botanica Hungarica 9. 1974 (Budapest, 1974)
Vida, László: Diatoms from a brooklet affluent to Arax river (Armenian Republic, USSR)
two hundred metres. Most of the springing waters dry up after a short flow leaving concrete-hard salt-mud in their beds, however, many hundreds of them arrive to the main flow of the river Arax. The latter are all named Arax by the people there, thus making distinction between the streams that flow through and those that dry up. The watercourse given in the title of this paper is a cataractous, very fast-running 4050 cm broad brooklet that floes into the main river. The sampling place was located about 500 m from the source. Here, after a small waterfall, a pool of about one square metre developed. MILKOVTTS sampled the material from the floating foam over the surface of that pool. The diatom material is therefore of secondary origin, but taking into consideration the impossibility of water flowbackdue to the gradient circumstances ant the closeness of the source there is no doubt that the mass of diatom shells, accumulated within the foam, characterizes properly the whole diatom vegetation of the uppermost 500 m section of the brooklet. METHODS The material of the water sample was prepared on 20 microscope spread slides with permanent embedding. The diatom frustules had to be cleaned of organic and inorganic impurities and of the live cell content as well, in order to make taxonomic identification possible. Cleaning was executed partly by heating the cover slip and the sample material dried over its surface to a red glowing state; partly by application of sulphuric acid. The material under examination remained rather stained even after the removal of organic components, therefore partly to segregate stain, partly to separate too dense shell material in order of size, 7 slides were made containing such material separated by increasing periods of sedimentation time . The embedding medium available to the author was Euparal with a rather low refraction index; however this is disturbing only in case of the most delicate diatom valves. For such cases 2 slides were prepared according to the so-called dry or mediumless technique. After the investigation, the diatom material left was preserved in distilled water conserved with 4 per cent formalin solution and was deposited together with the preparation slides to the coUecticn of the Botanical Department of the Natural History Museum. DISCUSSION OF DIATOM MATERIAL The investigated material contains 70 diatom taxa (species, variety, form). With respect to the very small quantity of the single sample, this is a rather high number. Of the identified diatoms there were 3 abundant, 6 frequent, 8 average, 16 sparse and 37 rare taxa, as regarding their frequency in the sample . The patterns of distribution of the taxa might be presented in a clearer way by the use of graphical delineation. If, in a system of coordinates, one axis bears the number of taxa and the other the logarithms of specimen numbers and one connects the values belonging together, the marking points of the sample in question, after correcting the standard errors caused by inexact estimation, will lie on a straight line. This is an evidence of the natural origin of the diatom material itself, too.
