Showing papers in "Journal of Phycology in 1970"

The effects of light and temperature on growth rates in boreal‐subarctic crustose corallines1

Abstract: SUMMARY A number of boreal-subarctic crustose corallines were kept in natural seawater tanks at temperatures ranging from 0 to 19 C and, using fluorescent lamps at light intensities, ranging from 7 to 750 lux with periods of 8 and 14 hr/day. The resultant growth rates as a function of temperature and light are presented and discussed in relation to the ecology of the plants. All of the Lithothamnieae studied had growth maxima at temperatures from 9 to 15 C. Growth in these species showed little light dependence below 4–6 C, but had a strong light dependence at higher temperatures. The one Lithophyllum species examined gave a flatter growth-temperature curve than the Lithothamnieae and showed little light dependence. The effects of temperature variation, salinity, and current on growth rates were also examined and are discussed. It was found to be especially important in studying growth rates of crustose corallines to allow time for growth stabilization following temperature change. In general, growth was found to exhibit a hysteresis effect, increased rates with the raising of temperatures 5–10 C and decreased rates with lowering temperatures.

The morphology and fine structure of ceratium hirundinella (dinophyceae)1

Abstract: SUMMARY Some aspects of thecal morphology in Ceratium hirundinella are redescribed by means of scanning electron microscopy. The internal anatomy of the cell has been clearly revealed for the first time in serial sections examined by transmission electron microscopy. An unusual sulcus, termed the sulcul aperture, has been found to open into a large ventral chamber which extends toward the center of the cell. The 2 flagella are inserted at one side of the ventral chamber. The ultrastructure of the flagellar canals and root systems arc described in detail. A microtubular strand has been found to run from near the nucleus to near the flagellar bases but not to conned with either. The fine structure of the theca, trichocysts, nucleus, and chloroplasts is basically similar to that of other dinoflagellates. Food vacuoles are reported. These contain material thought to be undergoing digestion. It is suggested that the food particles enter the cell by way of the ventral chamber, which is lined only by membranes, unlike the rest of the cell, which is covered by thick plates. The new findings are discussed in relation to the earlier work on the species and to the fine structure of oilier dinoflagellates.

Inorganic nitrogen assimilation of ditylum brightwellii, a marine plankton diatom1,2

Abstract: SUMMARY Apparent Km values for nitrite reductase, glutamic dehydrogenase, and nitrate reductase are of the order 10−4 molar for nitrite, ammonia, and nitrate, respectively while half-saturation constants for the corresponding uptake mechanisms approximate 10−6 molar. Ammonium and nitrate are accumulated in the vacuolated cells of the diatom (about 10 and 40 mmoles/liter cell volume, respectively) and these intracellular pools serve as substrate for the assimilatory enzymes. Nitrite is either not accumulated or is concentrated, in a very small cellular compartment. Ammonium and nitrate in the external medium exert modifying effects on uptake and assimilatory mechanisms which can be distinguished from effects of the ions accumulated within the cells. Several of these effects are described and fitted into a general scheme of nitrogen assimilation by D. brightwellii.

Mitosis, cytokinesis, and cell elongation in the desmid, closterium littorale1

Abstract: SUMMARY Some details of interphase cell structure are given. At prophase the nuclear envelope breaks down and the nucleolus disperses; very small doubled chromosomes generally form a precisely aligned, metaphase plate with normal spindle microtubules present; 2 plates of chromatids separate during anaphase, the spindle becoming invaded, by (mucilage) vesicles. Telophase nuclei arc initially very hard to discern, until they increase in volume. Microtubules collect at each pole, becoming increasingly focused on one small region containing fine granular malarial, the microtubule center (MC). The septum, an annular ingrowth, begins forming at prophase and partitions the cell by telophase. At no stage were microtubules involved in this initial cross-wall formation. At telophase the spindle collapses and as the nuclei move back to the septum, increasing numbers of microtubules appear near this cross wall, all transversely aligned. An annular split deepens down the middle of the wall material in the septum, and the daughter cells begin to expand, stretching the new wall; the microtubules appearing near the septum now are transformed steadily into typical hooplike wall, microtubules, but strictly confined to the expanding wall (there are none near interphase cell walls). Meanwhile, the MC, has moved, to the side of the cell and begins migrating along one of the grooves in the chloroplast; a large number of parallel microtubules extends back to the nucleus, which becomes increasingly deformed as it begins to extend a long thin protrusion along these, microtubules. The MC keeps moving along the cell until it lodges in the cleavage developing in the chloroplast. Some microtubules extend still further up the cell, others appear in the chloroplast cleavage, but most en-sheathe the nucleus which by now is moving along the cell as a cylindrical structure tightly fitting in the chloroplast groove. The nuclear membrane is then drawn up into the deepening chloroplast constriction, and when the chloroplast is finally cut in 2, the nucleus lakes up its interphase position between the 2 halves. While all this is occurring, the whole cytoplasm is expanding into the new semicell being created by growth of the wall originally derived from the septum. Thus the interphase cell symmetry is reestablished after mitosis. These results are discussed in terms of more general phenomena of cell division and morphogenesis.

Sexual reproduction in the dinoflagellate noctiluca miliaris suriray1,2

Abstract: SUMMARY The existence of sexuality in dinoflagellates has long been controversial. Events described as the differentiation and release of isogametes and sexual fusion in cultures of Noctiluca miliaris were studied with the light microscope. In cultures fed. twice weekly with Dunaliella sp., kept under a 12-hr day, 12-hr night light regime at 25–30 ft-c and held at 18 C, certain vegetative cells, termed gametocyte mother cells, were observed to undergo what is interpreted as meiosis. This was followed by several synchronous mitotic divisions occurring at 45-min to 1-hr intervals and. resulting in the production of up to 1024 mature uniflagellated isogametes attached on the surface of the gametocyte mother cell body. After several hours gametes now seen swimming freely in the media were observed to fuse and form zygotes. One zygote subsequently became vacuolated and eventually differentiated into a small but reasonably typical vegetative cell. The life cycle of N. miliaris appears thus to be of the diplontic type. The taxonomic relationships between Noctiluca and other mesocaryotic dinoflagellates are discussed.

Chloroplast division and pyrenoid formation in chlamydomonas reinhardi1

Abstract: SUMMARY The process of chloroplast division during mitosis in Chlamydomonas reinhardi is followed with the electron microscope. The pyrenoid and the chloroplast reproduce by fission. The dividing chloroplast contains regions of dense material that superficially resemble pyrenoids, but it is concluded that the formation of the dense material is not related to pyrenoid formation in C. reinhardi. The dense material appears to be localized over regions of chloroplast DNA.

Production of vitamin b12, thiamine, and biotin by phytoplankton1

Abstract: SUMMARY Some ecologically important phytoplankters released vitamins into culture medium during growth. Skeletonema costatum and Stephanopyxis turris (vitamin B12-requirers) produced both thiamine (vitamin B1) and biotin when growing with either 12 or 2 ng vitamin B12/liter. Gonyaulax polyedra (vitamin B12-requirer) produced thiamine with 12 ng vitamin B12/liter, and Coccolithus huxleyi (thiamine-requirer) produced vitamin B12 and biotin with 120 ng thiamine/liter, but only biotin with 10 ng thiamine/liter. The amount of vitamin produced by an alga and rate at which it was produced varied with the phytoplankter, the concentration of the required vitamin, and incubation time. Vitamins produced during early and exponential growth were due to excretions, and those produced at stationary growth resulted from excretion and release due to cell lysis. Uptake of the required vitamin by all phytoplankters was greatest during the first few days of incubation. On continued incubation the rate of uptake/cell decreased. In the sea phytoplankters may contribute a major portion of the amount of dissolved vitamins.

Vitamin production and utilization by phytoplankton in mixed culture1

Abstract: SUMMARY The production and utilization of vitamins by 2 or more, marine phytoplankters cultured in the same vessel were demonstrated. The release of toxic materials or vitamin inactivators wax also observed. The utilization of vitamins by those phytoplankters requiring them and the production of toxic materials were determined from increases and decreases in cell numbers of certain algae grown in mixed cultures. Vitamin utilization was most readily observed in mixed cultures where 2 phytoplankters were present. Dunaliella tertiolecta and Skeletonema costatum produced utilizable thiamine for Coccolithus huxleyi. C. huxleyi released utilizable vitamin B12 for Cyclotella nana. D. tertiolecta, Phaeodactylum tricornutum, and S. costatum produced utilizable biotin for Amphidinium carterae. The amount of utilizable vitamin and rate at which it was released depended on the phytoplankters present and conditions of incubation. In complex systems with more than 2 phytoplankters, beneficial effects to utilizers were often noted for short durations during the incubation period. At the end of the experiments the beneficial effects were usually not evident. P. tricornutum (nonvitamin requirer) was stimulated by a mixture of carryover B12 and thiamine when growing with A. carterae, indicating that in vitamin-free media it cannot synthesize vitamin(s) fast enough to allow for a maximum growth rate. The concentrations of vitamins in seawater samples may not be the amounts available to vitamin-requiring organisms. Among the factors affecting vitamin availability are the production of inhibitors and vitamin inactivators by various organisms in the ecosystem.

Surviving protoplasts in vitro and their development in bryopsis1

Abstract: SUMMARY In the coenocytic marine alga Bryopsis plumosa, extracellular protoplasts synthesize new cell walls in vitro and can develop into normal pinnate plants in the same way of the zygote of this species.

Dissolved organic phosphorus excretion by marine phytoplankton1,2

Abstract: SUMMARY The amounts of extracellular dissolved organic phosphorus (DOP) produced by 8 species of marine planktonic algae under various conditions of light, salinity, and nutrition were compared. Large amounts, more than 20% of the total P in the system, were excreted by Cyclotella cryptica, Thalassiosira fluviatilis, Dunaliella tertiolecta, and Synechococcus under 1 or more of the experimental conditions. Excretion of DOP was proportional to light intensity in Dunaliella, Rhodomonas, Chlorella sp., and Coccolithus huxleyi. Phosphorus limitation reduced DOP production by Cyclotella and Thalassiosira, nitrogen limitation reduced DOP production by Phaeodactylum, Dunaliella, and Rhodomonas, and lack of iron reduced DOP levels in Cyclotella cultures. Salinity affected growth, but no clear relationship to DOP excretion was evident. The DOP eliminated during growth was reassimilated by the species that produced it and by other species, but lack of alkaline phosphatase reduced the amount of DOP that was available to certain algae.

The growth and morphology of the silicoflagellate dictyocha fibula ehrenberg in culture1,2

Abstract: SUMMARY Dictyocha fibula was cultured in an enriched seawater medium from collections taken at Edmonds, Washington The optimum temperature for growth is 10 C at salinity 24% and 160 ft-c illumination in Provasoli enriched seawater at the concentration of 75 ml/liter seawater Average generation time is 49 hr In addition to swimming cells with skeletons, swimming cells without skeletons and nonswimming coenocytes were observed in clonal cultures at 15 C

Observations on the fine structure of the cryptophyceae. i. the genus cryptomonas1,2

Abstract: SUMMARY The fine structure of 3 members of the genus Cryptomonas, C. rostrella, C. reticulata, and C. calceiformis, has been examined. These species exhibit the features typical of the class Cryptophyceae. The presence of subpellicular trichocysts causes a regular folding of the periplast, and larger trichocysts are present within the gullet. The plastid contains thylacoids arranged in pairs and a prominent pyrenoid; both structures are enclosed in 4 membranes, the outermost of which is a rough endoplasmic reticulum. The nucleus, Golgi apparatus and the Corps de Maupas occupy characteristic positions within the cell, and are the most characteristic features. All these structures indicate that this algal class occupies a unique phylogenetic position.

Succession and current demand relationships of diatoms on artificial substrates in prater's creek, south carolina1,2

Abstract: SUMMARY A study concerning the colonization of glass slides by diatoms was conducted in Prater's Creek, Pickens County. S. C., to observe qualitatively and quantitatively the responses of the periphytic community to current velocities for varied lengths of time. Over short time periods (1, 2 and 4 weeks) diatoms seemed to adhere best at slow current velocities. Over longer periods (6 weeks) growth, of the initial colonizers seemed to be the density governing factor; consequently, the highest diatom densities developed at the higher current, velocities. The interaction of time and current resulted in a reversal of the diatom deposition phenomenon.

Field studies on the giant kelp nereocystis1,2

Abstract: SUMMARY An intertidal population of Nereocystis luetkeana was investigated in the field, and techniques for measuring sporophyte growth were developed. Primary regions of growth in plants prior to reproductive maturity were located in the bases of the blades, upper stipe, and holdfast. After reproductive areas on blades appeared, growth was confined to 2 major regions: the blade bases and the junction between lower stipe and holdfast where new holdfast haptera were produced. Complete deblading halted growth at whatever stage the plants had attained at the time of the operation but did not kill the plants. Partial deblading resulted in low but measurable growth rates in the blade bases. The data presented suggest that the function of the blades is twofold: they bear reproductive structures in the mature plants and. they may provide, materials used, in rapidly growing regions.

Cyanophyta‐bacteria systems: effects of added carbon compounds or phosphate on algal growth at low nutrient concentrations1

Abstract: SUMMARY Planktonic blue-green algae are known to be always associated with bacteria. Earlier work has shown that the addition of a bacteria-assimilable carbon source to a normal Zehnder-Gorham culture medium (No. 11) will produce enhanced growth of these algae when atmospheric CO2 has become the limiting factor. In new work, phosphate-rich culture media were diluted so that they simulated nutrient levels found in the Great Lakes, e.g., Lake Erie. At these low concentrations and when atmospheric CO2 was not available in a sufficient supply, the addition of sucrose to either a 1/100 or a 1/1000 diluted Z-G, medium (10 mg or 2 mg of sucrose, respectively) also produced enhanced, growth of the tested blue-green algae. The stimulation of algal growth was apparently due to an increased bacterial production of CO2 and possibly other carbon compounds approaching the composition of the CO2 molecule. The literature suggests that during vigorous algal growth in lakes, atmospheric CO2 will be severely limiting. Productive lakes always contain nonliving organic matter. The presence of bacteria-assimilable matter is probably one of the important factors leading to algal bloom.

The cell wall of pyrocystis spp. (dinococcales)1,2

Abstract: SUMMARY The cell of Pyrocystis spp. is covered by an outer layer of material resistant to strong acids and bases. Internal to this layer much of the cell wall is composed of cellulose fibrils. The presence of cellulose fibrils was established by staining raw and ultra-violet–peroxide-cleaned cell walls and by combining X-ray diffraction spectroscopy with electron microscope observation. Carbon replicas of freeze-etched preparations and thin sections of P. lunula walls show outer layers, inside them ca. 24 layers of crossed parallel cellulose fibrils (4–5 nm thick, ca. 12 nm wide), then a region of smaller (ca. 6–12 nm diameter) fibrils in a disperse texture, and then the plasma membrane. Cellulose fibrils in the parallel texture are constructed of 3–5 elementary fibrils ca. 3 nm in diameter. Walls of P. fusiformis and P. pseudonctiluca also have cellulose fibrils in a crossed parallel texture similar to those of P. lunula. The Gymnodinium-type swarmer from lunate P. lunula appears to have a cell wall ultrastructure typical of other “naked” dinoflagellates.

Autecological studies on the marine diatom rhizosolenia fragilissima bergon. i. the influence of light, temperature, and salinity1

Abstract: SUMMARY The influence of 113 combinations of temperature (9, 12, 18, 25, 30 C), salinity (5–35 ‰ at 5 ‰ intervals), and light (4 levels) on the mean daily cell division rate (K) of the Narragansett Bay clone of Rhizosolenia fragilissima was examined following appropriate preconditioning. Growth did not occur below 9 C, but was excellent (K =∼1.2) under certain combinations of light and salinity at 12, 18, and 25 C. The optimal salinity of 20–25 ‰ was temperature independent. Growth was not measurable at 5 ‰, although survival occurred. At 20 ‰ and 1200 ft-c, K increased approximately 1.8-fold from 0.65 to ∼1.2 between 9 and 18–25 C. The optimal light intensity was generally 600 ft-c, although several light-temperature-salinity trends were found. At 10 ‰ at all temperatures, the mean daily division rate decreased with increasing light above 600 ft-c, a response found at all salinities at 12 C, but not at other temperatures. Between 15 and 25 ‰, at 18 and 25 C, mean growth was independent of light intensity; at 30–35 ‰ a direct relationship with light may be present with maximum growth occurring at 1200–1800 ft-c. The in situ and in vitro responses of Rhiz. fragilissima to salinity and the optimum and upper temperature levels are in general agreement. However, growth failure below 9 C in vitro is at odds with reports that natural populations occur even at −1.11 C. The questions of to what extent this discrepancy reflects the occurrence of thermal clones, different taxa, and/or experimental artifacts are briefly discussed. It is suggested that naturally occurring populations found below 9 C might be designated as Rhiz. fragilissima f. faeroensis, and that Rhiz. fragilissima f. bergonii be used for populations growing at higher temperatures, until this matter is resolved. Observations on auxospore formation are presented.

Comparative studies in the genus porphyridium naeg.1,2

Abstract: SUMMARY Seven isolates of Porphyridium from 2 species were compared. P. cruentum Naeg. isolates were similar in size and pigmentation; differences were observed among the P. aerugineum Geit. isolates. Differences were detected among isolates in reproduction, rate of movement, growth rate, and sensitivity to CuSO4 and crystal violet. No isolate grew heterotropically; however, growth differences were apparent on various carbon sources.

THE ALGAE OF WAIMANGU CAULDRON (NEW ZEALAND): DISTRIBUTION IN RELATION TO pH1

Abstract: SUMMARY The pH of the main body of thermal water and of the outlet of Waimangu Cauldron (Frying Pan Lake) is 3.8, whereas hot springs flowing into this lake are alkaline, pH 8.2–8.7. Where these waters meet there are pH gradients, and it is possible to find a series of habitats differing in pH but having approximately the same temperature (54–56 C). Where the pH is above 4.8 the blue-green alga Mastigocladus laminosus is present, and where the pH is below this value the eucaryotic alga Cyanidium caldarium is the sole photosynthetic microorganism at temperatures less than 55 C. Rocks resting on the bottom of Waimangu Cauldron surrounded by water of pH 3.8 have Mastigocladus laminosus growing on them, but measurements of pH directly in these algal mats showed that the microenvironment of the alga was actually above pH 4.8. A simple experiment showed that it is probably the rock, per se, that initiates a tiny island of alkalinity in the acid lake, permitting M. laminosus to become established. The outlet of Waimangu Cauldron is a hot acid stream which becomes progressively alkaline as it descends through Waimangu Valley, due to inflow of alkaline water from springs and a cold stream. Blue-green algae were found in this stream when the pH was greater than 5.0 and C. caldarium when the pH was less than 4.0. In one region where the pH was between 4.0 and 5.0, both blue-green algae and C. caldarium were seen, although in moribund state. These data, provide further information on the lowest pH values at which blue-green algae are able to grow.

Evaluations of the availability of sources of nitrogen and phosphorus for algae1

Abstract: SUMMARY Techniques are compared for the evaluation of nutrient sources in which the potential nutrients are in contact with algae over their entire culture period versus relatively short-term exposure tests. Different nitrogen and phosphorus compounds were shown to be utilized in darkness as well as in light and were equally available at pH 7 and 9. The availability of relatively insoluble nutrients–iron-phosphorus compounds and teeth for phosphorus, hair for nitrogen iron pyrites for iron, and marble for carbon–indicates that in many cases the equilibrium between soluble and insoluble forms allows algae to compete successfully with insoluble forms for nutrients. Apparently, factors other than mere insolubility prevent algae from obtaining available nitrogen or phosphorus from phosphate rock or lake muds. Live algae or aquatic weeds with adequate or surplus nitrogen or phosphorus were shown to not share their nutrients with nitrogen- or phosphorus-limited algae, whereas the nutrients of killed algae or aquatic weeds were readily used by nutrient-limited algae. The facts–(1) that live algae and aquatic weeds do not share their adequate or surplus nutrients with nutrient-limited algae and (2) that lake muds do not provide readily available nitrogen or phosphorus–indicate that once lake waters are stripped of available nutrients by plant production, further plant production will depend upon nutrients from continuous sources of nutrients, such as wastewater effluents.

Requirements for the maintenance and growth of aphanizomenon flos-aquae in culture1,2

Abstract: SUMMARY Aphanizomenon flos-aquae has been introduced into unialgal culture in a completely defined medium and maintained for more than 3 years in the colonial flake form found in nature. The color and size of the flake and general appearance of the cells are substantially improved over those found in the original material at the time of collection from Upper Klamath Lake, Klamath County, Oregon. The alga readily forms both akinetes and heterocysts in culture Bacteria-free cultures have not been obtained. A precipitate-free medium designated ASM No. 8a has been developed from the ASM of McLachlan and Gorham. Their medium was altered by modifying the concentration of certain elements and by the addition of sodium bicarbonate, a 1/25 dilution of Arnon's trace element solutions B7 and C13, hydrogen ferric ethylenediamine di-o-hydroxyphenylacetate (EDDHA), and disodium ethylene dinitrilotetra-acetate (Na2EDTA).

Reproduction and systematics of the marine alga derbesia (chlorophyceae) in new england1,2

Abstract: SUMMARY The morphology, gross cytology, reproduction, and habitat ecology are described for Derbesia marina based on observations of New England field populations and laboratory cultures of this plant. These data, and additional observations on cultures of several other species of Derbesia from elsewhere and on type and other important collections, have been used to evaluate the systematic relationship of New England Derbesia with other species of this genus. The single Derbesia species in New England is referred to D. marina. The systematic criteria previously used to distinguish species within Derbesia are reviewed and interpreted within the context of the present investigation. In systematic studies, we stress the importance of the use of sporangial and chloroplast morphology, the presence or absence of pyrenoids, and reproductive history. Two types of life history are reported for D. marina in New England: (1) A form of D. marina collected at 20 m reproduces directly with stephanokontous zoospores growing into sporophytic plants of Derbesia morphologically identical to their parent thalli. (2) On the other hand, at least some New England, populations of D. marina have retained the genetic potential for producing a sexual generation (Halicystis ovalis), even though the latter is unknown for the coast of northeastern North America.3 Gametophytes (H. ovalis) were produced directly from enlargement and subsequent differentiation of uncleaved lateral sporangia in 2 cultured populations of New England D. marina. A single female and numerous male vesicles formed in this manner produced gametes, but neither fertilization nor parthenogenesis occurred; thus the entire life history was not completed in culture. The occurrence of the directly reproducing deep water form of D. marina is presented as evidence for speciation of a sporophyte (Derbesia) independent of its alternate gametophyte (Halicystis). An hypothesis is advanced to explain the source and means for expression of genetic variability necessary for speciation in a population of nonsexually reproducing Derbesia.

The crustose corallines of the northwestern north atlantic, including lithothamnium lemoineae n. sp.1

Abstract: SUMMARY Reproductive, vegetative, anatomical, and depth distribution keys are presented for the saxicolous crustose corallines of the northwestern North Atlantic. The 3 species of Lithothamnium in the region are named, while Lithothamnium lemoineae is described as a new species.

Taxonomy of chara braunii: an experimental approach1

Abstract: SUMMARY Results from the present study suggest that Chara braunii encompasses a complex of geographical races or incipient species that although morphologically similar, are isolated to varying degrees ranging from partial interfertility to complete reproductive incompatibility. Most of the 6 clones studied were interfertile to the extent that fertilization was followed by the development of black oospores, but subsequent germination tests disclosed that many of these either failed to germinate or gave rise to offspring that were partially or completely sterile. No support was encountered for the suggestion that C. braunii is of recent development or that it has been distributed rapidly throughout the world.

Frequent heterocyst germination in the blue-green alga gloeotrichia ghosei singh1

Abstract: SUMMARY A unique feature, frequent heterocyst germination, has been observed in a nonsporulating mutant clone (of spontaneous origin) of the blue-green alga Gloeotrichia ghosei Singh. The controlling factor seems to be the presence of ammoniacal nitrogen in the medium. In addition, such a medium supports differentiation of successive crops of new heterocysts and their germination in the name medium and in the same algal culture. Contrary to previous observations with oilier blue-green algae, ammoniacal nitrogen does not seem to inhibit heterocyst differentiation in this alga. Both the parent alga and its mutant clone grow poorly in a nitrogen-free medium, which, although they are not completely free from bacteria, may indicate that they tire poor fixers or nonfixers. However, they form a large number of heterocysts under these conditions. The general conclusion is that the heterocysts of blue-green algae show a multiplicity of structure and function. In the present case they have reproductive function leading to direct propagation of the alga. The bearing of these findings on the interrelationships of the genera Gloeotrichia and Rivularia has been discussed. It has been concluded that the distinction between them is purely artificial.

Volvox pocockiae, a new species with dwarf males1

Abstract: SUMMARY Volvox pocockiae is described as the second species in the section Janetosphaera. The somatic protoplasts are connected by cytoplasmic strands approximately the same diameter as flagella, and the construction of the spheroid is identical to that of V. aureus. Asexual reproduction by the division of gonidia differs from that in V. aureus in the enlargement of the gonidium prior to its division to form the embryo. Sexual reproduction is very similar to that in V. spermatosphaera, a species in the section Merrillosphaera without cytoplasmic connections. Dwarf males are formed in the posterior end of the parental spheroid, and, as in V. spermatosphaera, the dwarf males are composed exclusively of androgonidia with no sterile somatic cells. Females are facultatively asexual spheroids, the gonidia of which function as eggs. The single biflagellate zoospore produced by the germinating zygote undergoes cleavage to form a germling spheroid. The differentiation of gonidia in the asexual embryo and in the germling spheroid is evident only after inversion and enlargement of the spheroid have begun.

Glaucosphaera vacuolata, its ultrastructure and physiology1,2

Abstract: SUMMARY Glaucosphaera vacuolata was recently rediscovered, and isolated by Dr. Richard Starr of Indiana University Physiological and ultrastructural studies have been conducted on this cyanome and are reported for the first time. Glaucosphaera has been found to have low rates of photosynthesis, respiration, and Hill activity. Unusual features noted include the presence of R-phycocyanin as the major accessory pigment, phycobilisomes, and eyeshot-like structures in the cyanelles.

Aspects ultrastructuraux particuliers au plaste du batrachospermum virgatum (sirdt)—rhodophycée—nemalionale1

Abstract: SUMMARY Phycobiliprotein aggregates, found at the outer surfaces of the chloroplast lamellae of Batrachospermum virgatum, do not look like isolated globular granules, or thin discs, as reported in different algae by other authors. The aggregates appear as long cylinders of constant thickness, perhaps composed of subunits which are not distinguishable. On a single lamella (or thylakoid) the cylinders are always parallel to one another and this parallelism may persist through several successive lamellae. However, this pattern may change according to variations in the orientation of the lamellae; in tangential and oblique sections, the phycobiliprotein cylinders frequently take the shape of chevrons. In addition, arrays of tubular structures bearing phycobilin aggregates at their outer surfaces are also seen. These “tubes” probably originate from dilated short or fragmented thylakoids.

Stimulatory properties of filtrate from the green alga hormotila blennista. i. description1,2

Abstract: SUMMARY A laboratory phenomenon involving autostimulation of growth by filtrates of the green alga Hormotila blennista is described, and stimulation attributed primarily to the secretion of organic metabolites. Filtrates obtained from actively growing cultures 1 through 4 weeks old showed maximum growth rate stimulation values in excess of 100%. Stimulatory properties of filtrate were heat labile, were not closely controlled by the starting pH within the limits normally encountered in culture, and did not result from depletion of essential nutrients. Concomitant with growth rate stimulation, filtrates characteristically extended the lag phase of culture growth. H. blennista filtrate can support bacterial growth and selectively stimulate or inhibit 2 planktonic green algae. It was suggested that extracellular organic products secreted by H. blennista during active growth could be of survival value to the organism, and could also play regulatory roles among other microorganisms in nature.

Studies on the photobiology of bangia fuscopurpurea1

Abstract: SUMMARY In the Rhodophyta there are few reports of light-mediated responses. In Bangia fuscopurpurea the formation of the fertile cell rows by the Conchocelis phase meets criteria established for the definition of photoperiodism in higher plants. Throughout the life history of the alga maintained in culture, cell fate and cell function fire under photoperiodic regulation. Maintenance and conversion photoperiods are established. Sequential induction studies suggest the absence of metabolic effects operative in the induction, response of fertile cell row formation. Preliminary studies of non-24-hr photoperiods suggest the absence of short-term endogenous rhythms involved in spore formation. A phytochrome response involved in the formation of the fertile cell rows is demonstrated.