Postoji li Thiosiphon

U svojoj obradi begijatoaceja u Bergcyevu manualu determinativnc bakteriologije v a n N i e l je posumnjao u valjanost roda Thiosiphon (Klas 1936). Kao razlog za to svoje mišljenje navodi: razlike u veličini goniđija, do kojih je došao usporedivši u originalnom opisu podatke u tekstu s mikrofoto- grafijama; upadljivu sličnost, koju pokazuje Thiosiphon s vrstom Beggiatoa mirabilis u nekim kulturama i sličnost goniđija ti osi fona s pripadnicima roda Achromatium. Laka povredljivost poprečnih membrana, poteškoće njihova promatranja u nitima krcatim sumporom, gotovo sigurna prisutnost ahromacija na staništu tisifona i samo rekonstruirani razvojni ciklus opravdavaju po van N i e 1 ovu mišljenju znatno sumnjao je u valjanost roda. Autor se ne slaže s van N i e 1 ovim gledištem oslanjajući se na podatke literature, koje van Niel nije uzeo u obzir, kao i na prigodna vlastita opažanja. Razlike u veličini goniđija na mikrofotografijama i u tekstu proizlaze vjerojatno iz različitog shvaćanja pojma »povećanja«. S vrstom Beggiatoa mirabilis (B. gigantea) Thiosiphon ne može se zamijeniti, jer Beggiatoa niti je polarno građena, niti je pričvršćena na supstrat. Prema autorovu mišljenju bi se oštećenja, koja bi uništila poprečne membrane, morala bez daljeg prepoznati. Osobito se ne može mimoići postojanje \u27poprečnih membrana u fiksiranim i bojenim preparatima (usporedi navode D el ap o r t e-ove 1939), a ni kod primjeraka, u kojih je sumpor bio uklonjen oksidacijom ili otapanjem, što je navedeno i u originalnom opisu (str. 210). Od ahromacija razlikuju se gonidije tiosifona, osim po obliku i strukturi, i time što su negibljive, a promatranje njihova razvoja predstavlja znatne poteškoće. Autor smatra polaritet i nedostatak poprečnih membrana karakteristikama, koje jasno dokazuju, da <se radi o posebnom organizmu, a koje prema tome opravdavaju i postavljanje novoga roda

A new locality of Wolffia arrhiza in Croatia

Wolffia arrhiza (L.) W i m m, was found in large masses associated with Spirodella polyrrhiza (L.) S c h l e i d, in an old branch of the river Sava near Zagreb. A precise description of the habitat is given in the above Croatjan text. In the parts of this dead branch, which was totaly dried up during the summer, it was also possible to establish the presence of a great many shoots of Wolffia and Spirodella. In the mud the presence of living shoots of Wolffia and Spirodella could still be found in the depth of nearly 5 cm and even more. Tho shoots of Wolffia were summer and winter shoots as well, but those of Spirodella were\u27 on the contrary exclusively winter shoots. Wolffia arrhiza (L.) W i m m. was known in Croatia till now only from 3 localities, which all are in the territory of Quarner. The new finding-place, the first in the inner continent of Croatia, represents a connection-point between the localities of Quarner and those of Baika, Panievo (Serbia) and Roumania, thus connects, to a certain extent, the Roumanian-Serbian spreading territory with the Quamerian one. In Slovenia, Austria and Hungaria an occurrence of Wolffia is not known

Echinocystis lobata. A new adventatous plant of the Croatian Flora

Echinocystis lobata was found near Voloder (Kutina, Croatia). This, for the Croatian flora new adventitious plant, seems to be already spreaded in Croatia (in Moslavina and Posavina territory) in a considerable extent. In Slovenia its spreading was stated before by V. PctkovSek in the years 1945—1949. This Northamerican Cucurbitacea was probably spread into Slovenia from Austria, where it was stated some years ago (Fritsch 1922, Hegi 1931) and then penetrated into Croatia undoubtedly along .the Sava- river

Chloroplast structure and function in wild-type and aurea-type leaves of the Japanese spindle-tree over their life span

The evergreen leaves of the Japanese spindle-tree (Euonymus japonicus Thunb. \u27Aureomarginatus\u27) are adapted to endure repeated freezing and thawing during the winter. We investigated the physiological and morphological characteristics of the chloroplasts in young, overwintering, and overwintered wild-type and aurea-type leaves. When developing in the shade, both leaf types during their life span maintained a well-developed thylakoid system in their chloroplasts. The photosynthesis rates were also similar. When growing in intense sunlight, the aurea variety contained chloroplasts with a reduced thylakoid system, but photosynthesis was less reduced. In spring, overwintered leaves of both varieties clearly showed ultrastructural and physiological characteristics of senescence. The senescence in aurea leaves exposed to full sunlight was more pronounced

Structural changes of lamellar cells in leaves of the moss Polytrichum formosum Hedw. during winter freezing and thawing processes

The lamellar cells of winter leaves of Polytrichum formosum were studied by electron microscopy of thin sections, and the results were compared with those for spring and summer plants. Pigment content and photosynthetic activity were also analysed. The lamellar cells of winter plants, when grown at temperatures above zero, had a similar ultrastructure to those of spring and summer plants. Their pigment content and photosynthetic activity were also similar. On the other hand, the lamellar cells of frozen plants (examined at temperatures about –5 °C) were desiccated, i.e. deformed, the cytosol was shrunken, and the ribosomes and mitochondria were aggregated. The thylakoid system of their chloroplasts was irregularly arranged and the grana thylakoids were compressed. The desiccation of the cells was soon annulled when the ambient temperature rose above zero

Paleogeographic evolution of the Southern Pannonian Basin: 40Ar/39Ar age constraints on the Miocene continental series of notthern Croatia

The Pannonian Basin, originating during the Early Miocene, is a large extensional basin incorporated between Alpine, Carpathian and Dinaride fold-thrust belts. Back-arc extensional tectonics triggered deposition of up to 500-m-thick continental fluvio-lacustrine deposits distributed in numerous sub-basins of the Southern Pannonian Basin. Extensive andesitic and dacitic volcanism accompanied the syn-rift deposition and caused a number of pyroclastic intercalations. Here, we analyze two volcanic ash layers located at the base and top of the continental series. The lowermost ash from Mt. Kalnik yielded an 40Ar/39Ar age of 18.07 ± 0.07 Ma. This indicates that the marine-continental transition in the Slovenia-Zagorje Basin, coinciding with the onset of rifting tectonics in the Southern Pannonian Basin, occurs roughly at the Eggenburgian/ Ottnangian boundary of the regional Paratethys time scale. This age proves the synchronicity of initial rifting in the Southern Pannonian Basin with the beginning of sedimentation in the Dinaride Lake System. Beside geodynamic evolution, the two regions also share a biotic evolutionary history: both belong to the same ecoregion, which we designate here as the Illyrian Bioprovince. The youngest volcanic ash level is sampled at the Glina and Karlovac sub-depressions, and both sites yield the same 40Ar/39Ar age of 15.91 ± 0.06 and 16.03 ± 0.06 Ma, respectively. This indicates that lacustrine sedimentation in the Southern Pannonian Basin continued at least until the earliest Badenian. The present results provide not only important bench marks on duration of initial synrift in the Pannonian Basin System, but also deliver substantial backbone data for paleogeographic reconstructions in Central and Southeastern Europe around the Early–Middle Miocene transition

A new locality of Wolffia arrhiza in Croatia

Wolffia arrhiza (L.) W i m m, was found in large masses associated with Spirodella polyrrhiza (L.) S c h l e i d, in an old branch of the river Sava near Zagreb. A precise description of the habitat is given in the above Croatjan text. In the parts of this dead branch, which was totaly dried up during the summer, it was also possible to establish the presence of a great many shoots of Wolffia and Spirodella. In the mud the presence of living shoots of Wolffia and Spirodella could still be found in the depth of nearly 5 cm and even more. Tho shoots of Wolffia were summer and winter shoots as well, but those of Spirodella were\u27 on the contrary exclusively winter shoots. Wolffia arrhiza (L.) W i m m. was known in Croatia till now only from 3 localities, which all are in the territory of Quarner. The new finding-place, the first in the inner continent of Croatia, represents a connection-point between the localities of Quarner and those of Baika, Panievo (Serbia) and Roumania, thus connects, to a certain extent, the Roumanian-Serbian spreading territory with the Quamerian one. In Slovenia, Austria and Hungaria an occurrence of Wolffia is not known