Giacomo Tripodi

Thallus morphology and spore formation in cultured Erythrocladia irregularis rosenvinge (Rhodophyta, Bangiophycidae)

The discoid thallus of Erythrocladia irregularis is the result of a pattern of cellular divisions expressed by mono‐and endospores; the latter are described for the first time in Erythrocladia. In nutrient enriched growth conditions the discoid thallus becomes a shapeless aggregate of unicells with a wrinkled wall surface, whose plane of division is unpredictable. The cells are able to produce monosporangia with a curved wall or they form eight‐celled endosporangia. Chloroplasts have an internal pyrenoid, as is characteristic of the Erythropeltidaceae.

Structure and reproduction of Gracilaria longa sp. nov. (Rhodophyta, Gigartinales) from the Mediterranean Sea

Abstract Gracilaria longa sp. nov. is described from the Mediterranean Sea, after a comparison of habit, morphology and reproduction with other species from the same area. The species is characterized by elongate second order axes, slender ultimate branchlets, «verrucosa-type» spermatangial conceptacles, a lobed fusion cell and a poorly developed inner pericarp. Karyological observations on meiotic tetrasporangia showed that n=24. A comparison with other Mediterranean species of Gracilaria with terete thalli is presented. The morphological similarities between some species of the genus in the Mediterranean are considered to be a result of low evolutionary divergence due to a relatively recent origin.

A study on Gracilaria dendroides sp. nov. (Gigartinales, Rhodophyta) from the Bay of Naples

Gracilaria dendroides sp. nov. is described from the Bay of Naples, Italy, where it thrives on the rocks in the upper littoral. The species has a typical branching pattern resulting in the dendroid habit of the plant. G. dendroides is also characterized by lanceolate branchlets which become longer and taper in the distal part of the branches. Tetrasporangia, spermatangial conceptacles and cystocarps are localized in the lanceolate branchlets. The cortex in which tetrasporangia are deeply immersed is modified, the cells being less vacuolized and with a thick cell wall. The spermatangial conceptacles are as in G. verrucosa. The gonimoblastic tissue is lobate with connective filaments to the pericarp. The morphological and structural features are considered stable thus supporting the description of a new species.

Unusual structures in the spermatial vesicles of the red algaErythrocystis montagnei

Electron microscopic observations on the membrane of the spermatial vesicles in the red algaErythrocystis montagnei are presented. A portion of this membrane is modified and more electron dense, with a layer of microtubules of about 20 nm. Generally, this membrane portion forms two paired bulges, appearing 3-shaped in cross-section. More rarely, two completely separate cylindrical bodies of about 0.3 µm diam. surrounded by membranes have been observed in the spermatial vesicles. The significance of these structures as possible vestigial remnants of flagella is discussed.

ELECTRON MICROSCOPY OF MEMBRANOUS BODIES AND GENOPHORE IN CHLOROPLASTS OF BOTRYOCLADIA BOTRYOIDES (RHODYMENIALES, RHODOPHYTA)1

An ultrastructural study on the chloroplasts of the red alga Botryocladia botryoides(Wulfen) J. Feldmann has been carried out to investigate the morphology of globular membranaous bodies (MBs) located between thylakoids. These membranous bodies show an electron dense lumen, in which a pair of denser cores occasionally occurs. The lumen is electron transparent in the chloroplasts of vacuolized, non‐dividing cells. The surface of MBs is in contact with the fibrils representing the plastidial genophore; the fibrils sometimes bridge the surface of MBs with the nearest thylakoid. In some planes of section a membranous stalk connecting a MB with thylakoids has been made evident.

Osservazioni Ecologiche Su Alcune Alghe Del Golfo di Napoli in Relazione Alla Loro Distribuzione Verticale

Abstract Ecological observations dealing with some seaweeds of Bay of Naples in connection to their vertical zonation. — The algal zonation in a basaltic locality of the Bay of Naples was studied by the A. in order to get some data about the environmental requirements of seaweeds living in that locality. He pointed out the vegetation girdles of: a) « Bangia fuscopurpurea », « Gelidium pusillum », « Nemalion helmintoides » in the supra-littoral belt; b) « Corallina mediterranea » and « Enteromorpha compressa » in the eu-littoral belt; c) « Pterocladia capillacea », « Scytosiphon lomentarius », « Callithamnion granulatum » and « Derbesia tenuissima » in the infra-littoral belt, studied to 70 cm below the water mark. All these belts are overlapped by that of « Porphyra leucosticta ». « Bangia fuscopurpurea » seems to have a scarce adaptability, since it vegetates exclusively on the rocks spraied by the waves, but never submerged, so that this girdle is very large only in the more exposed localities; this sea...

Cytoplasm views from the Devonian: Observations on cells of Rhynia gwynne-vaughanii

Abstract A light microscopy study of a vascular plant (Rhynia gwynne-vaughanii) of the Lower Devonian period fossilized in the Rhynie chert (NE Scotland), allowed for observations of uncompressed tissues, with minute cytological features, some of which have not been reported before in the literature. In a few cells of the outer cortical parenchyma a slightly shrunken cytoplasm was observed, stretched in thin strands, on which granules of around 1 μm are visible. The latter could represent mitochondria or lipid droplets. When the surface of the cytoplasm is focussed, granules of about 4 μm are visible, and these may be interpreted as chloroplasts. A dark rounded structure with fading contour, about 20 μm in diameter, was observed in the core of the cell and was interpreted as the nucleus. The cytological details suggest that both physical and chemical factors stopped the decaying process in these cells in a sudden and efficient way, and that a rapid silicification followed fixation. There was intense volcanic activity in the Rhynie region in the Lower Devonian era, and this included lightning and hot gaseous releases, both of which could have caused the death of the entire biological community, later fixed in the chert. The mechanism of preservation of biological structures is discussed in the light of the recently proposed role of lightning in the rapid fixation of plant tissues.

Una Struttura Comparabile Con I Lomasomi Nelle Cellule Austoriali di Cuscuta Pentagona Engelm

Abstract A structure comparable with the lomasomes in baustorial cells of « Cuscuta pentagona » Engelm. — Electron microscopic observations of haustorial cells in « Cuscuta pentagona » revealed to the A. the presence of some vesicular structures, outside the plasma membrane, comparable to the lomasomes of Moore and McAlear. The vesicles usually group in a bag of the plasma membrane and show an envelope consisting of unit membrane; their shape and size are variable and some of them are not well distinct while some others show ribosome-like bodies inside .In the examined cells the plasma membrane shows prominences which are in connection with the vesicle membrane, so that the A. thinks it possible the derivation of the vesicles from the peripherical cytoplasm. The function of these structures is not yet explained; they are only found in non photosyntetic cells, such as some Mycophyta, dark grown « Avena » coleoptiles and dodders haustorial cells. The previously ultrastructural researchs on dodder have not ...