Showing papers in "American Journal of Botany in 1940"

Studies on chlorella vulgaris ii. further evidence that chlorella cells form a growth-inhibiting substance

Abstract: PREVIOUS STUDY of the growth of the unicellular green alga Chlorella vulgaris showed that under the conditions employed the maximum density of population attained in different cultures is independent of the size of the inoculum, that the rate of multiplication throughout the growth period in different cultures varies inversely with the initial density of population, and that the rate of multiplication, as measured by the increase in number of cells per hour per cell in a given culture, decreases during nearly the entire period of growth (Pratt, 1940). It was pointed out that the data could be interpreted as affording evidence of the presence of a growth-inhibiting substance that was produced by the cells. If such an agent is liberated into the culture medium as the result of the metabolic activities of the cells, it should be possible to measure its effects by studying the increase in the population of cultures prepared with media in which some growth has already occurred. Further experiments and data bearing on this subject are presented herewith. MATERIALS AND METHODS.-General.-The experimental technique was essentially the same as that which was previously employed except that in the present work cell counts were made less frequently than in the earlier work and were obtained by averaging haemacytometer counts of two samples withdrawn from single cultures instead of four samples taken from triplicate cultures. The values obtained in the present work approximated reasonably closely those obtained for comparable cultures in the detailed earlier work. Unless otherwise stated, cells for all experiments were taken from four-day-old, rapidly growing stock suspensions and were washed in three changes of distilled water by repeated centrifugation and decantation. Preparation of nutrient media.-A number of cultures were prepared as previously described (Pratt, 1940) with an initial population of 100 cells/cu. mm. and were permitted to grow for different lengths of time. The culture solution was prepared with distilled water and contained KNO3, 0.025 M.; MgSO4 7H21, 0.02 M.; KH2PO4, 0.018 iLI.; FeSO4 7H20, 0.00001 M.; potassium citrate 0.00001 M.; and Zn, 0.1 ppm.; Mn, 0.1 ppm.; B, 0.05 ppm.; and Cu, 0.001 ppm. A gas mixture containing 5 per cent CO2 and 95 per cent air was bubbled continuously through the solutions, and the cultures were illuminated continuously by Mazda lamps yielding about 20,000 lux at the level of the flasks. The temperature at the level of the flasks was about 200C.?20. At suitable intervals several of the cultures were centrifuged and the supernatant solution was drawn 1 Received for publication March 20, 1940. through sintered Jena glass filters, number 1 G 4. The filtrate was then used, either diluted or undiluted according to the experiment, to prepare new nutrient solutions. Since it was not feasible to analyze the different solutions to ascertain the precise amount of each salt that had been removed during the growth period, uniform quantities of the salts employed were added to each solution and the pH was adjusted by the addition of H2SO4 to 4.45, the pH of similar media prepared with distilled watpr.2 The total salt concentrations were not unifor jm in all solutions, therefore. The minimum concentration was 0.063 M. (media prepared with distilled water). The maximum concentration could not have exceeded 0.12 M. (media prepared with 90 per cent filtrate and 10 per cent distilled water), and may have been considerably below that value. In no instance was there any evidence of growth over a period of two weeks in uninoculated media so prepared. It may be concluded, therefore, that the treatment effectively removed all cells. EXPERIMENTS AND RESULTS.-Influence of concentration of nutrient solution on the growth of Chlorella.-Since the concentrations of the salts in the different solutions were not identical, it seemed desirable to ascertain the influence of the concentration of the culture medium on growth. Figure 1 shows the results of this investigation. It is evident that the variations in concentration were not significant for the work reported below, since the total molar concentration of the nutrient medium exerted relatively little influence on the rate or amount of growth of Chlorella between 0.01 M. and 0.1 M. The inset shows that the final cell counts in solutions containing 0.01 mole and 0.1 mole per liter were 97 and 95 per cent, respectively, of those in the standard control solution which contained 0.063 mole per liter. The several salts and the micrometabolic elements were furnished in the same proportions in each solution. Only the total concentration was varied. In preliminary experiments it was found that fair growth occurred in filtrate diluted to twice its original volume with distilled water. This seems to afford ample evidence that depletion of nutrients is not a primary factor in determining the final level or gradually decreasing slopes of growth curves of Chlorella cultured under the experimental conditions employed. However, since it was found that the concentration of the standard solution could be doubled without seriously impairing growth, the filtered medium was fortified in the present work by an addi2 As growth proceeds in the standard solution employed in this work, the pH value rises from an initial level of 4.45 to approximately 6.5-7.0.

Carbon dioxide reduction with molecular hydrogen in green algae

Abstract: HYDROGEN HAS been used very often as a means to replace air in experiments with plant material when anaerobic conditions were desired. No effects of this gas on the metabolism of plants other than those observed in an atmosphere of nitrogen have been reported. Hydrogen has been considered, therefore, as an inert gas for the plant. (For references see Spoehr, 1926; Stiles, 1936.) This paper furnishes the experimental evidence of a new type of photosynthesis which can be induced artificially in some strains of algae belonging to the genera Scenedesmus and Rhaphidium. Under the proper conditions the photochemical reduction of carbon dioxide will proceed with the simultaneous absorption of twice the volume of molecular hydrogen. The reaction bears a striking resemblance to the photosynthesis with hydrogen found a few years ago in purple bacteria. (Roelofsen, 1934; Gaffron, 1935; French, 1937.) METHODS.-The plant used in most of the experiments was the alga Scenedesmus spec. D 3. Rhaphidium,2 which gave similar results, appeared to be more easily injured by the experimental procedure. The algae were grown in absolutely pure cultures. Culture methods and general properties of the alga have been described elsewhere (Gaffron, 1937, 1939b, 1940). The gas exchange was measured manometrically; 0.05 to 0.200 ml. of cells were suspended in 2 to 4 ml. of a bicarbonate or phosphate solution. The gas space of the manometer was filled either with air, N2, 02, H2, or with the same gases containing approximately 4 per cent C02, according to the special experimental conditions. The light sources used were a 1,000 W. incandescent lamp and a specially constructed neon lamp. The neon lamp was a frame, somewhat larger than the thermostat window, completely filled with parallel tubes of commercial neon sign tubing. Light of shorter wave length than 5,500 A' was filtered out by a sheet of red cellophane. The intensity of illumination could be changed in a measurable way with the aid of gray glass filters from Schott and Gen. Jena. The relative ratios of the different intensities given in figure 2 are accurate within a few per cent. (See Gaffron, 1937.) The absolute value of the intensities is only approximately correct. It was measured with an ordinary photronic 1 Received for publication December 18, 1939. The experiments reported were made at Hopkins Marine Station, Pacific Grove, California, where the author was the guest of Dr. C. B. van Niel to whom he feels greatly indebted. The manuscript has been kindly read by Dr. F. Rieke. A short communication has appeared in Nature, Vol. 143, 204, 1939. 2 Dr. Yamanouchi was kind enough to identify the alga as Rhaphidium polymorphium var. aciculare. cell as used in photography. No effort has been made to correct the values found in respect to the color sensitivity of the photo-electric cell. In the experiments reported only the relative intensities are of iinportance. The diameter of the neutral glass filters, however, was so small that only two vessels could be illuminated simultaneously. Later therefore the glass filters were exchanged for sheets of colored commercial cellophane large enough to cover the entire front window of the thermostat. The number of red filters was increased until the visible spectrum did not change in quality by the addition of two more filters. Under these conditions green cellophane filters could be used practically like neutral gray filters to changc the intensity of the light without altering its spectrum. For measurements of the dark metabolism, the manometer vessels were wrapped in tinfoil and the thermostat covered with a lid and black cloth. Under aerobic conditions the gas exchange in the dark is due to respiration; under strictly anaerobic conditions to fermentation. In computing the light metabolism, corrections have been applied accordingly. But it is sometimes difficult to decide which kind of dark reactions prevail when photosynthesis begins under anaerobic conditions and, by producing oxygen, changes these conditions gradually into aerobic ones. As a rule in the following experiments a correction for respiration has been made only where so much oxygen had been liberated by the illuminated cells that a true, measurable respiration resulted. Whether or not an oxygen partial pressure below one per cent of an atmosphere is sufficient to maintain normal respiration is still a matter of controversy. Generally the respiratory quotient begins to rise at very low oxygen pressures because additional carbon dioxide is formed due to the beginning of fermentation. From the point of view of the method of measuring the gas exchange, the terms liberation, formation, production, etc., of oxygen by photosynthesis should be used only if oxygen gas escapes from the cell and can be found outside of it. As long as we have no means of distinguishing between free and bound oxygen (photoperoxides) inside the cell, it is meaningless, for instance, to say that the plant produces molecular oxygen which is consumed instantly and completely by respiration in such a way that only the formation of carbon dioxide can be observed. This practical attitude appears to be particularly justified in the case of the microscopically small unicellular algae. Contrary to widespread belief, the oxygen partial pressure inside these cells depends less on their photochemical activity than on the oxygen concentration of the surrounding me-

Influence of the size of the inoculum on the growth of chlorella vulgaris in freshly prepared culture medium

Abstract: THE IMPORTANCE of the unicellular green alga, Chlorella vulgaris, to plant physiologists engaged in studies of cellular metabolism and especially of photosynthesis is well known Relatively few detailed studies have been made of its growth, however The present paper deals with the growth curve of Chlorella in cultures inoculated with different numbers of cells taken from parent cultures of the same age Multiplication, or increase in cell number, was used as an index of growth in this work, although it is realized that a period of cell enlargement precedes each division, and that growth is the result of these two processes MATERIALS AND METHODS-Cells for the experiments were withdrawn from four-day-old, rapidly growing stock suspensions of Chlorella vulgaris cultured asg previously described (Craig and Trelease, 1937; Pratt and Trelease, 1938) in a solution that contained KNO3, 0025M; MgSO4 7H20, 002M; KH2PO4, 0018M; FeSO4 7H20, 000001M; potassium citrate, 000001M; and Zn, Cu, B, and Mn in approximately the concentrations employed by Trelease and Trelease (1935) The initial pH of this solution was 445 New stock cultures were started daily so that there was always available a supply of cells of approximately the same physiological age and activity Cells were separated from the culture medium and were washed in three changes of distilled water by repeated centrifugation and decantation They were then suspended in distilled water and the density of the population in the suspension was estimated from haemacytometer counts Inocula containing the desired number of cells were pipetted into 500 ml Pyrex glass Florence flasks, each of which contained 150 ml of the standard nutrient solution The flasks were continuously illuminated from below by a water-cooled battery of twentyfour 50-watt frosted Mazda lamps The light intensity, measured by means of a Weston photoelectric-cell light meter, Model 603, varied from 21,000 lux to 18,000 lux The lamps were replaced by a complete new set when the intensity fell below this value The temperature at the level of the flasks varied from 18? to 220C A gas mixture containing 5 per cent CO2 and 95 per cent air was bubbled continuously through the solutions The cultures were shaken vigorously twice daily to insure separation and uniform suspension of the cells Growth measurements were made periodically by withdrawing small samples from each flask and estimating the cell population from haemacytometer counts Triplicates of each culture were prepared, 1 Received for publication November 27, 1939 The author is indebted to Miss Jane Fong for valuable assistance in the laboratory and cell counts were based on the averages of haemacytometer counts of four different samples from each flask Each point in the figures represents, therefore, the average of twelve samples The maximum deviation from the mean value occurred in the lower portions of the growth curves and never exceeded 5 per cent Over the major portion of the curves in all cultures the deviation of individual cultures from the mean value was less than 3 per cent EXPERIMENTS AND RESULTS-Figure 1 shows the growth in cultures inoculated with different numbers of cells withdrawn from parent cultures of the same age Since the points describe sigmoid curves, it seemed of interest to examine the data to ascertain whether they could be represented by the equation characteristic of autocatalyzed monomolecular reactions that has been found, in many cases, to describe reasonably well the growth of populations and of individual organisms (Ostwald, 1908; Robertson, 1908a, 1908b, 1923; Reed and Holland, 1919; Reed, 1920, 1921a, 1921b, 1928a, 1928b, 1932; Gaines and Nevens, 1925; Porterfield, 1928; Pratt, 1936) The differential form of this equation expresses the rate of growth, and may be written

Comparative host ranges of six plant viruses

Abstract: THE FAILURE of viruses to multiply except within living cells has led to considerable speculation regarding the essential materials or conditions necessary for their reproduction. Holmes (23) recently approached the problem from the standpoint of the taxonomic affinities of plant species found to be susceptible or insusceptible to tobacco-mosaic virus (Marmor tabaci H.).2 He found that classification of tested species of plants into four groups according to their natural relationships revealed a group consisting of only susceptible species, a group of largely susceptible species, a group made up of about half susceptible and half insusceptible species, and a group of mostly insusceptible species. Holmes suggested that there may be an orderly distribution in nature of substances or conditions necessary for multiplication of the virus. If this interpretation is correct, other plant viruses might show a similar tvpe of host distribution. A comparison of the host ranges of several plant viruses might lead to a knowledge of certain differences and similarities in specific chemical or physical properties required bv viruses for reproduction. With this idea in mind, plants belonging in a large number of families have been tested for susceptibility to six different viruses. The results of the tests are presented herewith. MATERIALS AND METHODS.-Virus stocks.-The following plant viruses were used: Tobacco-necrosis virus (Marmor lethale H.). Cucumber-mosaic virus (M. cucumeris H. var. vulgare H., judicis H., and vignae H.); most tests were made with the ordinary strain, vulgare. Cucurbit-mosaic virus (M. astrictum H. var. aucuba H.). Alfalfa-mosaic virus (M. medicaginis H. var. typicum Black and Price). Tobacco-ringspot virus (Annulus tabaci H. var. virginiensis H.). Tomato-ringspot virus (A. zonatus H.). The table to be considered presently includes results of other workers with additional virus strains. Most of these strains are listed in the Handbook of Phytopathogenic Viruses (24). One strain not listed there but included in the table is the potato-calico strain of alfalfa-mosaic virus (Marmor medicaginis var. solani Black and Price), only recently shown to belong in the alfalfa-mosaic virus group (7). The virus stocks were transferred to young plants at frequent intervals in order to insure a high virus content in the juices to be used as inoculum. Cucumber (Cucumis sativus L.) served as a source plant for cucurbit-mosaic virus, Turkish tobacco (Nicotiana tabacum L.) as a source plant for the other

Studies on the nutrition of fungi. iv. factors influencing the growth of some thiamin-requiring fungi

Abstract: THE NECESSITY of an extraneous supply of thiamin for the growth of many fungi has been definitely established, but we know comparatively little concerning the influence of a number of contributory factors upon the growth of such organisms. The present investigation is an attempt to extend our knowledge concerning these factors. Part I of this paper concerns itself with the agar factor; Part II with the effect of organic acids upon nitrogen utilization; and Part III with nitrogen-dextrose-thiamin ratio. TECHINIQUE.-Unless otherwise stated, all cultures were grown on 25 ml. of nutrient solution in Erlenmeyer flasks of 250 ml. capacity. The basic medium consisted of 0.5 gram each of ammonium nitrate, potassium dihydrogen phosphate, magnesium sulfate, 5 grams of Bacto-Dextrose of highest purity, 0.5 gram of a mixture of amino acids (d-arginine, d-glutamic acid, 1-aspartic acid, 2 parts each, and 1 part each of glycine and dl-a-alanine), Robbins and Kavanagh's (1938) modification of Hoagland's A-Z mixture of rare elements, and 1,000 ml. ,of distilled water. This solution, as well as all its modifications, was adjusted to pH 5.5 by means of sodium hydroxide. The amount of auxithals varied according to the nature of each experiment. The foregoing solution containing 1/100th ppm. thiamin was solidified by 2 per cent agar, and 15 ml. of it was poured in a series of 90 ml. Petri dishes. These were autoclaved and inoculated with the various test organisms to furnish the necessary stock cultures. All flasks were inoculated by means of inoculum discs cut from the vigorously growing Petri dish colonies by means of a cork borer with an opening of 5 mm. in diameter to insure inoculum pieces of uniform size and vigor. All cultures were made in quintuplicate and incubated at 25?C. for various lengths of time. The crop was then harvested, and five mycelial mats in each series were comI Received for publication October 16, 1939. Published with the approval of the Director of the West Virginia Agricultural Experiment Station as Scientific Paper No. 227. bined and dried at 100?C. to constant weight. Thus each figure given in the following tables, unless otherwise stated, represents the composite weight of five cultures. The actual weight of mycelium obtained under controlled conditions has been made the criterion for the evaluation of the comparative effectiveness of various factors. However, it should be emphasized that biological phenomena cannot be reduced to mathematical figures without making a generous allowance for the frequent and often disconcerting fluctuations that characterize the behavior of living things. No matter how rigidly one mav control the environmental conditions and repeat a given experiment, one will always find some differences in the weight of the crop. Even the different cultures of the same experiment made at the same time and under identical conditions will continue to vary. We have found that such variations may be from 5 to 10 per cent; however, this is not great enough to be significant.

The oxygen consumption of isolated woody tissues.

Abstract: ALTHOUGH THE respiration of woody stems has been studied by a number of investigators (Devaux, 1899; Ruhlanid and Ramshorn, 1938; Moller and MlUller, 1938; et al.), information concerning the gas exchanges taking place in the different tissues composing stems is still fragmentary. This is due chiefly to difficulty in isolating woody tissues in a relatively undamaged state and in measuring accurately the small gaseous exchanges taking place between these tissues and their environment. The present investigation represents an attempt to overcome these difficulties. Quantitative measurements of the rate of oxygen consumption of different woody tissues have been made under aerobic conditions. MATERIALS AND METHODS.-The experiments reported in this paper were carried out on black ash, Fraxinus nigra L., and red maple, Acer rubrum L. The trees were collected in the spring of 1939 at Riga, New York, where bud break occurred between May 5 and May 10 for these species. Data as to their ages, dimensions and dates of collection are given in table 1. Eight-foot sections of the tree trunks were brought to the laboratory, and the freshly-cut surfaces were paraffined in order to reduce desiccation between experiments. The trunks were stored at outside air temperatures. The tissues used in the following experiments were taken from the trunks 20 to 50 cm. above the ground level. The rates of oxygen consumption of the phloem and of the cambial zone on a series of days after collection, shown in table 1, indicate that no significant differences in rate occurred in tissues from the stored trunks over a period of 15 days. The tissues were cut with a very sharp knife on a Thomson-Jeffrey sliding microtome in order to reduce to a minimum injury to the uncut cells. The sections were approximately 0.1 mm. thick, allowing ready diffusion of gases (Warburg, 1923) and rather precise segregation of tissues. Sections of the phloem, cambium and newly-formed xylem (about 10 X 20 mm.) were cut as nearly as possible in the 1 Received for publication January 19, 1940.

The morphology of the flowers of the juglandaceae. ii. the pistillate flowers and fruit

Abstract: THE PARTS of the "floral envelope" and other features of flower structure and fruit of the Juglandaaceae have been subjects of much discussion. In the flowers of some genera the "floral envelope" consists of seven parts, in other genera of one to three parts. DeCandolle (1862), Eichler (1878), Engler (1889), Nicoloff (1904-1905), Rendle (1925), and most other European authors consider the seven parts a bract, two bracteoles (Vorbliitter, prefeuilles, prophvlls, foreleaves) and 4 sepals. Nagel (1914) agrees in this interpretation only for the pistillate flowers. Britton and Brown (1913), Bailey (1924), and Gray's New Manual of Botany (1908) call the parts calyx and corolla in either the family or the generic description (Juglans) or both, though Britton gives the possibility of their interpretation as a bract, two bracteoles, and a 3-5 lolbed (normally 4-lobed) calyx. The four parts of the "floral envelope" of the pistillate flowers of Carya are described by most authors as a bract, two bracteoles, and a calyx lobe, by other writers as four calyx lobes. The present writer has attempted to settle this difference of opinion by a careful comparison of the "floral envelopes" of most of the species of all genera in the family. This study has not only made the nature of the floral members in Juglans more definite, but has shown also that there is more variation in the number of parts of the flowers in some genera, has thrown new light on the nature of the floral leaves of Engelhardtia, Car ya, and Platycarya-, has shown more variation in the stigmas of En-gelhardtia, and has revealed new structures in the flowers of Juqlans and Carya. In this paper the author attempts to bring up to date the description of the pistillate flowers and fruit of all six genera of the family, illustrating as many of them as possible, thereby laying a foundation for a discussion of the structure of the flowers of the pre-Juglandaceae, and of the evolutionary tendencies within the family. The present article, a succeeding one on the staminate flowers, and the previous one by the writer (1938a) on the 1 Received for piblication April 25, 1940. Contributions from the Department of Botany, Smith College, New Series, No. 6. The writer wishes to express appreciation to the curators of the herbaria at the New York Botanical Garden, U. S. National Herbarium, Arnold Arboretum, and the Gray Herbarium for their generosity in loaning specimens, to Dr. Holttum of the Botanic Gardens, Singapore, Dr. Hochreutiner of the Conservatoire et Jardin Botaniques, Geneva, Dr. Metcalf of the Botanical Survey, Lingnan University, Canton, China, and others for their kindness in sending preserved material, and to Prof. Frances Grace Smith of Smith College for her friendly advice and criticism in the writing of this paper. The drawings were made by Grace Petersen. inflorescence will provide a background for his future papers on the anatomy of the flowers and on the generic characters that can be used in separating the different genera. NATURE OF THE "FLORAL ENVELOPE."-In this paper the term "floral envelope" will be used for all of the floral leaves, whatever their character. The interpretation of Eichler and of Engler will be followed as to their nature; namely, bract, two bracteoles, and four sepals; one or more sepals and even the bracteoles may be lacking or modified. The evidence for this interpretation will be presented under Pterocarya and in the later discussion. The nature of the parts in the pistillate flowers is clearer than in the staminate flowers, and the structure more constant. The bract and bracteoles are variously fused with the pedicel and the ovary, thus appearing as part of the "floral envelope." The sepals, if present, are always united with the ovary. Pterocarya (fig. 1-6, 53).-The pistillate flower of Pterocarya shows most clearly the structure of the parts of the "floral envelope." These are in three, or seemingly in two, whorls: a tiny anterior bract, two broad lateral bracteoles, the latter surrounding and united with the base of the ovary, and four small sepals, fused with the ovary for two-thirds of its h ight. During development of the flower, the bract remains small, but the bracteoles enlarge, at least the posterior portions being carried up with the ovary in its growth. Thus the fruit is a small, broadly two-winged nut (fig. 107-109). The bract is ciliate, longer, and more leaf-like, in P. rhoifolia, P. insignis, and related species than in P. fraxinifolia and P. stenoptera. In P. Paliurus the bracteoles are fused into one nearly complete wing (fig. 109). Rehder and Wilson (1917) pointed out that this wing consists of two structures, and is therefore not essentially different from the wings of the other species. The number of sepals is typically four, buit the writer has seen a few flowers of P. fraxinifolia with five sepals, occasionally with a tiny petal (?) or stamen (?) opposite one of them. Five to six "sepals" occur rarely in the flowers of P. Paliurus. The flowers of P. stenoptera are still more variable. Five "sepals" occur frequently, especially in flowers having three carpels; six "sepals" were found in some of the three-carpelled flowers, and seven "sepals" in one two-carpelled flower (Manning, 1926). The sepals in these flowers were usually unequal in size, irregularly arranged; and in some cases one of these structures, probably an abortive stamen, occurred in a whorl inside that of the rest. In Pterocarya the bract and bracteoles cannot possibly be called sepals. As DeCandolle (1862)

New marine algae from southern california. ii

Abstract: FURTHER STIJDY of the marine plants of Soutlhern California (cf. Hollenberg, 1940, 1943) brings to light additional plants wlich seem not to lhave been previously reported. Several of these are described herewith. Griffithsia multiramosa (Setchlell and Gardner) T'aylor, (Neomonospora multiramosa Setchlell and Gardner, 1937) var. balboensis, var. nov. (fig. 1). Plantae rosaceorubrae aut lucidae rubra, cristas delicatas et globosas et 10-15 cm. crassis formnantes, fere epiplhyticae, implicatae et dense ramnosae; ramis multo dichlotomo ramosis; 150-170 t crassis deorsum et gradati'm angustioribus sursum ad 30 t aut minus; segmnentis fere 10-18 diametros longis, et minus ad apicem ramorum, leviter tumidis; tetrasporangiis sparsis, globosis et 60-70 t crassis, tetralhedralibus divisis, sine ramis involucralibus, singulatim per pediculum fere unicellulare affixis; cystocarpiis et raimiis antlheri(lialibus ignotis. Plants rose-red to deep red in color, forming delicate globular tufts mostly 10-15 cm. in diameter, epiplhytic or often unattaclhed, intricately and densely branclhed; branclhes repeatedly dichlotomous at a very narrow angle except in lower parts, 150-170 t in diameter and witlh relatively tlhick walls below and gradually narrower above to 30 t or less, witlh tlhin walls; segments mostly 10-18 diameters long and shlorter toward the tips of the branclhes, only slightly tumid; tetrasporangia infrequent, globular and 60-70 t in diameter, tetrahedrally divided, witlhout involucral branches, attaclhed singly mostly at non-forking nodes by a short pedicel of one or two cells, so that a tetrasporangial branclh forms one branclh of a dichotomy; sexual plants unknown; plants occurring in sheltered water of inland bays. The type specimen of this plant is number 2364, tetrasporic, collected by the writer, September 24, 1938, near the bridge of State Highway No. 101, where the upper bay connects witlh the harbor proper at Balboa, Orange County, California. It has been repeatedly collected at this place where it is sometimnes very abundant and either floating free in the tidal current or attached insecurely to various objects. This plant has been collected by various investigators a number of times at different places in Southern California over a period of many years, but is rarely found in fruit. The scarcity of reproductive structures may bear some relation to the seeming readiness witlh wlichl the plant propagates vegetatively. Rhizoids arise witlh considerable frequency from the branclhes and the writer is inclined to believe that fragmentation followed by ready formation of rhizoids results in vegetative propagation, although no experiments have been performed in this conneetion. 1 Received for publication May 10, 1945. G. multiramosa var. balboensis is very close to G. multiramosa var. minor described by Taylor (1939) from Baja California, Mexico. The local plant is muclh larger and differs in its more globular form and frequently free-floating lhabit, and especially in labitat, since it seems to be confined to the warm water of slheltered bays and lagoons. From the species as described by Setchlell and Gardner ( 1937) the plant differs in the tetralhedral division of the sporangia and in lhabit and lhabitat. It also seems close to G. arachnoidea described by C. Agardlh (1828) from the coast of "Gallea" and figured by B0rgesen (1930). Judging by Agardlh's description, and by the figures and description of B0rgesen, the California plant differs in the more globular form and less tumid cells. I"lants collected by B0rgesen were from exposed positions. Soutlhern California plants seem to be decidedly limited to warm, slheltered bays. CHONDRIA arcuata sp. nov. (fig. 2-i) Frondes pullo rubrae et cristatae, cum rainis prostratis et repentibus per intervalla frequentia per lhapteres breves et robustos ad saxa affixis et cum ramis erectis 3-4 cm. altis et 300-400-(700) t crassis; ramnis perspicue arcuatis, ad fundainentum attenuatis et fere cum rainulis paucis et similiter arcuatis; ramis manifeste polysiplhonis, cum quinque cellulis pericentralibus comnparate magnis, longitudine aequali; segmnentis axis pericentralibus fere 1-1.5 diametros longis; cortice tenui circiter stratorum duorum cellularum 20-25 t crassis et 1.0-1.5-(4) diamnetros longarum constructo; apicibus crescentibus in puteis in apicibus ramorumn truncatorum positis, et cristam trichloblastarumn breviumn et dense furcatarum ferentibus; tetrasporangiis in apicibus ramorumn sitis, 8090 t crassis, tripartitis; cystocarpiis ovoidis et sessilibus, circiter 360-450 t crassis, sine calcaribus in basi; ramnulis antlheridialibus orbicularibus numerosis ad apices ramorum, 180-215 j latis. Fronds dull red, tufted, witlh prostrate creeping branclhes attaclhed to rocks by slhort sturdy lhapteres at frequent intervals and erect terete branclhes 3-4 cm. hiiglh and 300-400-(700) t in diameter; branclhes conspicuously arcuate, attenuate at the base and mostly witlh few or no branclhlets, the branclhlets being simnilarly curved; branches conspicuously polysiplionous internally, witlh five relatively large pericentral cells of uniform lengtlh slhowing plainly tlhrouglh the relatively tlhin cortex and giving an evidently segmented appearance to the brancles witlh respect to the inner core; segments of the pericentral axis cotnposing more than lhalf of the widtlh of the branches and 1.0-1.5 diameters long; cortex mostly of 2-3 layers of cells 20-25 t in diameter and 1.01.5-(4.0) diameters long; clhromnatoplhores in the form of long, contorted bands; growing point of