HYBRIDIZATION OF MACROCYSTIS (PHAEOPHYTA) WITH OTHER FLOAT-BEARING KELPS1,2

Sporophytes were produced in 22 out of 23 attempts to cross Macrocystia angustifolia Bory with Pelagophycus porra (Lemon) Setchell. Representative samples of these plants were raised in a surge-tank under greenhouse conditions to several meters in length. The plants resulting from this intergeneric cross were intermediate in morphology between the parental genera. The intermediate plants were similar to those found fry one of the authors (MN) in 1957, and by others since then, in California kelp beds where Macrocystis and Pelagophycus co-occur, A cross between M. angustifolia and Nereocystis luetkeana (Mertens) P. & R., also produced normal sporophytes. The taxonomic, evolutionary, morphogenetic and genetic implications of these hybridizations are discussed.     

GROWTH OF BLADES OF NEREOCYSTIS LUETKEANA (PHAEOPHYTA) IN DARKNESS 1

Short term measurements were made of the relative growth rate of the fast growing portions of blades of Ncreocystis luetkeana (Merl.) Post. et Rupr. during exposure to natural daylight and during prolonged darkness. Growth was only slightly, but significantly, faster during the 12 h of daylight than during the 12 h that included 8 h of darkness. Clearly considerable growth occurred at night. In blades amputated 1 cm beyond the zone measured, growth was slower during both night and day. In continuous darkness growth continued for up to 12 days. It was not influenced by amputation of distal blade tissue but it was increased by severance from the bulb and stipe. A mean volume increase of 50% of the blade tissue was recorded. While the organic content decreased, the drop was half that required to support the increase in volume. There was some evidence against translocation. It is possible that cellular biochemical rearrangements allow a light-independent increase in organic material.     

OBSERVATIONS ON THE LIFE HISTORY OF PAPENFUSSIELLA CALLITRICHA (PHAEOPHYCEAE,CHORDARIALES) IN CULTURE1

Papenfussiella callitricha (Rosenv.) Kylin from eastern Canada was studied in culture. Zoids from unilocular sporangia develop into microscopic, filamentous, dioecious gametophytes which produce isogametes in filament cells and few-chambered plurilocular gametangia. Unfused gametes germinate to reproduce the gametophytes. Fusion takes place between a settled (“female”) and a motile (“male”) gamete. The zygote gives rise to a filamentous plethysmothallus that reproduces asexually by zoids formed in thallus cells and in few-chambered plurilocular zoidangia. Erect macrothalli are produced on the plethysmothallus, beginning with the formation of upright filaments. Later on, these filaments become the terminal assimilators of the macrothalli. Further assimilatory filaments, rhizoids, and unilocular sporangia are produced in a branching region at the base of the terminal assimilator. Zoids from unilocular sporangia formed in culture germinate to reestablish the gametophyte phase. Chromosome counts yielded n = 19 ± 3 for the gametophytes, and 32 ± 6 for the sporophyte, both plethysmothallus and macrothallus.     

Apomeiosis inAcinetospora (phaeophyceae,ectocarpales)

Acinetospora crinita from the Mediterranean Sea has been studied in laboratory cultures. The plants formed monospores and unilocular sporangia. Both monospores and zoids from unilocular sporangia developed to new plants with the same habitus and chromosome number (average ca 47). This indicates that meiosis in unilocular sporangia fails, and that sexuality has been lost in the cultures studied. It is concluded that loss of sexuality is the cause of the great variability and establishment of distinct geographically isolated populations in the genusAcinetospora.     

The specific identity and the life history of JapaneseSyringoderma (Syringodermatales,phaeophyceae)

Observations on JapaneseSyringoderma from Rishiri Island, which had been previously identified asS. australe, were made based on newly collected fertile material. These results and comparisons with the type specimen ofSyringoderma abyssicola (=Chlanidophora abyssicola) revealed that the Rishiri Island plants should be identified asSyringoderma abyssicola. Syringoderma abyssicola from Rishiri Island formed unilocular sporangia among the paraphyses on the fan-shaped blades in winter. The first products (uni-spores) in the unilocular sporangia form flagella, and soon after form cell walls before release. Then these reduced gametophytes divide into tetrads and form swarmers, each of which contains a chloroplast with a stigma. These swarmers germinate into branched filaments, from which thicker erect filaments of apical growth tissue. At 5–10 C these erect filaments formed fan-shaped blades under long-day conditions, and unilocular sporangia under short-day conditions corresponding respectively to spring and winter at Rishiri Island. Accordingly, the seasonal growth pattern of the species is considered to be controlled by responses to photoregime and temperature. Dedicated to the memory of the late Professor Muneao Kurogi.     

THE SPORANGIUM OF HORNEOPHYTON LIGNIERI (RHYNIOPHYTINA)

Numerous sporangia of Horneophyton lignieri from the Rhynie Chert locality in Scotland have been studied. The sporangia are branched, with two to four columellate lobes of varying length, and a continuous sporogenous zone or cavity occurs among the lobes. Unbranched sporangia, generally thought to be the typical form for the plant have not been found, and their presence is not established. Although not definitely proven, evidence suggests that the sporangia opened by means of a small apical pore or stoma. An area of thick-walled cells at the apex of each sporangial lobe probably played some role in this opening. Radial, trilete, azonate spores ranging from 39–49 μm in diam, with curvaturae perfectae are produced most commonly in tetrahedral tetrads and occasionally in isobilateral tetrads. Matters of spore preservation and possible ornamentation are discussed. The branched sporangia of this genus are unique among bryophytes and vascular plants and provide some evidence that certain synangia may have arisen from a single sporangium rather than from multiple sporangia borne singly at the tips of ultimate branches.     

PATTERNS OF RELATIVE GROWTH IN NEREOCYSTIS LUETKEANA (PHAEOPHYTA)1

Plants of Nereocystis luetkeana (Mert.) Post. et Rupr. of different sizes were held on a raft at the surface of the sea, off the Friday Harbor Laboratories, San Juan Island, Washington for 5-day periods for obseruation of detailed relative growth of different parts. Each stipe was marked at intenlals with injected Indian ink and each blade was punched with a series of holes. Measurements of diameter, length, width and thickness were made before and after the 5-day periods. Blades showed a very similar pattern of relative growth rate (R) ovler an 18-fold range of sizes. The maximum local R in length was about 0.2 day⁻¹ and occurred at 6.5% of the distance from the bulb to the tip, declining to 0.01 at half way. Half the linear growth occurred in the proximal one tenth of the blade and 95% within the proximal half: The relative growth rate of the whole blade declined only slightly with increased size and lay between 0.03 and 0.06 day⁻¹ (approx. 3-6% day⁻¹). The linear growth rate therefore increased with blade size, the maximum observed being 14 cm day⁻¹. The maximum relative growth rate in blade width was slower, and sited more distally than that in length. Unless fertile tissue was involved all blade tissue, except that closely adjoining the bulb, became thinner duringgrowth. R in volume reached 0.3 day⁻¹. Presumably because the plants were held near the sea surface stipes grew slowly, with a maximum linear rate of 9 mm day⁻¹. The maximum R in length decreased with stipe length. Bulb R in volume also decreased as size increased, from a maximum of 0.3 day⁻¹.     

The absolute configuration of the flagellar apparatus in zoospores from two species ofLaminariales (Phaeophyceae

Summary We examined the zoospores produced by the unilocular sporangia ofLaminaria digitata (L.) Lamour. andNereocystis luetkeana Post. & Rupr. by serial sectioning to determine the absolute configuration of their flagellar apparatuses. The basal bodies, which are interconnected by three striated bands, lie parallel to the ventral face of the zoospore, and the posterior basal body always is found to the right of the anterior basal body when the cell is viewed from the ventral face, anterior end up. The four rootlets associated with the basal bodies include a major anterior rootlet of about seven microtubules extending from the anterior basal body along the ventral face towards the apex, a five-membered bypassing rootlet that passes ventral to the basal bodies and is connected to the posterior basal body by a posterior fibrous band, and two short rootlets having a single member each, the minor anterior and posterior rootlets. We consider the configuration observed here to be typical of most phaeophycean motile cells. The flagellar apparatus features suggest a considerable phylogenetic difference between thePhaeophyceae and other classes of chlorophyll c-containing organisms.     

Morphology and life history of Scytosiphon canaliculatus comb. nov. (Scytosiphonales,Phaeophyceae) from Japan*

Morphology of field material and life history in culture were studied in Scytosiphon canaliculatus (Setchell et Gardner) comb. nov. from northern Japan. Erect gametophytes of S. canaliculatus are cylindrical, tubular, up to 7 mm wide and 40 cm long, and without regular constrictions. S. canaliculatus has pronounced anisogamy and ascocysts accompanied with plurilocular gametangia. The life history of S. canaliculatus showed an alternation between erect gametophytes and crustose prostrate sporophytes bearing unilocular sporangia. Since field sporophytes of S. canaliculatus were found to be identical with Hapterophycus canaliculatus Setchell et Gardner (Ralfsiaceae, Phaeophyceae), it is proposed to transfer H. canaliculatus to the genus Scytosiphon. In the field, gametophytes with plurilocular gametangia appeared in spring and disappeared in summer. Sporophytes with unilocular sporangia were collected in late autumn and winter. Unilocular sporangia were produced at 15°C in short-day culture conditions and unispores developed into erect gametophytes at 5–15°C. It is suggested that the seasonal Occurrence of gametophytes in the field is due to the seasonal formation of unilocular sporangia, which is regulated by temperature and photoperiod.     

LIFE HISTORY AND SYSTEMATIC POSITION OF AKKESIPHYCUS LUBRICUS (PHAEOPHYCEAE)1

The life history in culture of Akkesiphycus lubricus Yamada et Tanaka, an alga which has been placed in the Coilodesmaceae or the Punclariaceae, Dictysiphonales, was studied. In culture the species alternates between a microscopic filamentous gametophyte and a macroscopic polystichous sporophyte, a pattern common to the Dictyasiphonales and Laminariales. However, it has a unique anisogamous dioecious gametophyte. Fusions between mac-ro-gametes and micro-gametes were not observed, Macro-gametes or zygotes germinated, mostly developing into sporophytes that formed unilocular sporangia and the rest developed into reduced gametophytic flaments again. The gametophyte matures in 50C short-day conditions, corresponding to winter in Hokkaido. The sporophyte develops normally and matures only in low-temperature conditions irrespective of daylength. In regard to iits systematic position, Akkesiphycus lubricus is considered to have a closer relationship with the Laminariales than with the Dietyosiphonales in the following characters; lack of pyrenoids; early stages of parenchyma formation in the sporophyte; direct development of sporophytes from gametes or zygotes without forming a besal system zoospore becomes almost empty after germination by the migration of cell contents into a germ lube; formation of macro-gametangia by direct conversions of mother cells of mother cells of fertile branches; and micro-gametangia formed in clusters showing closeresemblance to the antheridia of Pseudochorda nagii (Tokida) Inagaki.     

On the sexual reproduction ofDictyosiphon foeniculaceus (Phaeophyceae,Dictyosiphonales)

Dictyosiphon foeniculaceus from Sweden and Newfoundland was studied in laboratory culture. Zoids from unilocular sporangia developed into dioecious microscopic filamentous gametophytes which produced uniseriate plurilocular gametangia in low temperatures (0 to 8 °C). Zygotes and unfused isogametes gave rise to filamentous protonemata on which parenchymatous macroscopic sporophytes were formed. Isolates from Sweden and Newfoundland were interfertile. Although formed in culture, genetically unisexual sporophytes were not detected in nature. Female gametes ofD. foeniculaceus produced a sexual pheromone. It was identified as finavarrene, which is also known as the sperm attractant inAscophyllum nodosum.     

The ship-fouling algaEctocarpus

Summary The unilocular reproductive stages of the brown algaEctocarpus have been examined with the electron microscope. One observation in particular, which is believed to have been made for the first time in Phaeophycean studies, is that the zoospore derived from unilocular sporangia possesses a microanatomy considerably different from that of spores formed by plurilocular sporangia. It is suggested that this difference may have an evolutionary significance and may lead to a better understanding of the life cycle ofEctocarpus.     

LIFE HISTORY OF COLPOMENIA SINUOSA (SYCTOSIPHONACEAE,PHAEOPHYCEAE) IN THE AZORES1

Colpomenia sinuosa (Mertens ex Roth) Derbès and Solier (Scytosiphonaceae, Phaeophyceae) is a common species on the rocky intertidal shores of the Azores, where reproductive gametophytes occur throughout the year. Life‐history studies of this species were carried out in culture, and both sexual and asexual reproduction were observed. Anisogamous gametes fused to form zygotes. The zygotes gave rise to a filamentous prostrate sporophyte generation bearing unilocular sporangia, under both short‐day and long‐day conditions at 15 and 22°C, and to both unilocular and plurilocular sporangia, under the lower temperature condition. Unispores developed into gametophytes, and plurispores gave rise to filamentous sporophytes. Asexual reproduction was carried out by unfused female gametes and asexual plurispores produced from the same gametophyte. Unfused gametes developed into filamentous prostrate sporophytes producing unilocular sporangia in both culture conditions, and unispores released from the sporangia gave rise to gametophytes. Asexual plurispores from field gametophytes, under both culture conditions, developed directly into new gametophytes. The species exhibited three types of life history: a heteromorphic, diplohaplontic; a heteromorphic, monophasic (both with alternation between the erect and filamentous prostrate thalli); and a monomorphic, monophasic.     

Life history of Japanese Stypocaulon durum (Sphacelariales, Phaeophyceae)

Phenology, morphology, life history and responses to different temperature and photoperiod conditions were studied in Japanese Stypocaulon durum (Ruprecht) Okamura. Erect thalli of the species were collected year-round, but the mature thalli forming either uniloc-ular sporangia or two different types of plurilocular structures (evidently gametangia) on separate thalli were found only in winter. ln culture, an isomorphic life history is suggested for the species, alternating between a sporophyte forming unilocular sporangia and gam-etophytes forming plurilocular macro- (female) and micro- (male) gametangia. Contents of unilocular sporangia were not released, but germinated in situ, developing into erect thalli forming plurilocular gametangia. Macrogametangia released aplanogametes (oospores), but male gametangia appeared to be non-functional, although flagellated cells were once formed in the loc-uli. This is the first report of plurilocular gametangia in the species. Although the species grew well and matured under considerably lower temperature conditions than European Stypocaulon scoparium (L.) Sauvageau, its temperature requirements showed similarity to northwestern Atlantic Stypocaulon species. This supports the notion that northwestern Atlantic Stypocaulon is conspecific with S. durum.     

MORPHOLOGY AND LIFE HISTORY OF SCYTOSIPHON LOMENTARIA (SCYTOSIPHONACEAE,PHAEOPHYCEAE) FROM THE AZORES1

Morphological and culture studies of Scytosiphon lomentaria (Lyngbye) Link and Microspongium gelatinosum Reinke (Scytosiphonaceae, Phaeophyceae) were undertaken on material collected on the Island of São Miguel, Azores, where both species were commonly found. Erect thalli of S. lomentaria collected in the field were up to 33 cm long and 2.3 mm wide, tubular, hollow, and commonly constricted at intervals. The plurilocular sporangia were positioned in continuous sori on the thallus surface. Ascocysts were present. In the field, M. gelatinosum formed crustose to slightly pulvinate plants, were spongy in texture, and dark brown to black in color, which were circular or irregularly spreading over several centimeters and firmly attached to the substratum. Sessile unilocular sporangia were located in sori on the crust surface. In culture S. lomentaria plurispores developed into Microspongium‐like crustose prostrate thalli that formed unilocular sporangia. Unispores developed into new erect thalli that formed plurilocular sporangia. Sexual reproduction was not observed. In culture, M. gelatinosum unispores developed into erect thalli identical with S. lomentaria. These results are similar to those reported for other areas and suggest the occurrence in the Azorean plants of a monophasic and heteromorphic life history, involving both entities studied.     

Morphology and life history of Halopteris filicina (Sphacelariales, Phaeophyceae) from Korea

The vegetative morphology and life history of Halopteris filicina (Grateloup) Kutzing, collected from Korea, were examined in laboratory culture. Field plants attaining 3–5 cm in height were epilithic, tufted, yellowish-brown, and produced numerous erect axes with alternately distichous branches from compact basal discs. They were cultured under a 12:12 h LD photoperiod at 10°-C, 15°C and 20°C to observe the influence of temperature on reproduction. At 10°C plants grew only vegetatively, whereas at 15°C and 20°C they produced unilocular sporangia. Unispores released from sporangia developed into monoecious, anisogamous gametophytes that formed plurilocular female and male gametangia on the same lateral branches. The zygotes, by fusion of female macrogametes and male microgametes, developed into sporophytes bearing unilocular sporangia, whereas the unfused female gametes germinated parthenogenetically. This species was confirmed to have an isomorphic life history, basically similar to the other species of Sphacelariales.     

Experimental evidence against sexual fusions of spores from unilocular sporangia of Ectocarpus siliculosus (Phaeophyta)

Evidence that sexual fusion does not occur in zoids from unilocular sporangia of Ectocarpus siliculosus is presented as follows: (1) Zoids from various types of unilocular sporangia do not interact with genuine gametes; (2) Aggregates of two zoids, previously claimed to be zygotes, were frequently seen in cultured material but could be demonstrated to be the result of incomplete cell separation during sporogenesis; (3) Culture studies showed that there is no fusion of male and female nuclei in such aggregates.     

COORDINATNE NUCLEAR AND CHLOROPLAST DIVISION IN UNILOCULAR SPORANGIA OF LAMINARIA ANGUSTATA (LAMINARIALES,PHAEOPHYCEAE)1

Changes in the number of nuclei and chloroplasts were examined during the process of unispore formation in unilocular sporangia of Laminaria angustata. Just before meiosis, eight chloroplasts were always present in unilocular sporangial mother cells. The number of chloroplasts remained constant through meiosis. After the resulting four nuclei divided again (third nuclear division), a close association between a nucleus and a chloroplast developed among each of the eight nuclei and eight chloroplasts. The eight chloroplasts divided ahost synchronously before the synchronous division of the eight nuclei. Following the 16 nucleate stage with 16 chloroplasts and the final 32 nucleate stage with 32 chloroplasts, 32 unispores, each with a nucleus and a chloroplast, were fomd in unilocular sporangza of L. angustata. Immunofluorescence microscopy using an anti-centrin antibody showed that two anticentrin-stained structures (as future mitotic poles) occurred adjacent to each of the premitotic four nuclei, and each spot was located near a chloroplast. Therefore, after the third division, each of the eight nuclei established close contact with a chloroplast presumably mediated by the centrosomes.     

PATTERNS OF RELATIVE GROWTH IN NEREOCYSTIS LUETKEANA (PHAEOPHYTA)1

Plants of Nereocystis luetkeana (Mert.) Post. et Rupr. of different sizes were held on a raft at the surface of the sea off the Friday Harbor Laboratories, San Juan Island, Washington for 5 day periods for observation of detailed relative growth of different parts. Each stipe was marked at intervals with injected Indian ink and each blade was punched with a series of holes. Measurements of diameter, length, width and thickness were made before and after the 5 day periods. Blades showed a very similar pattern of relative growth rate (R) over an 18-fold range of sizes. The maximum local R in length was about 0.2 day⁻¹ and occurred at 6.5% of the distance from the bulb to the tip, declining to 0.01 at half way. Half the linear growth occurred in the proximal one tenth of the blade and 95% within the proximal half. The relative growth rate of the whole blade declined only slightly with increased size and lay between 0.0.3 and 0.06 day⁻¹ (approx. 3–6% day⁻¹). The linear growth rate therefore increased with blade size, the maximum observed being 14 cm day⁻¹. The maximum relative growth rate in blade width was slower, and sited more distally than that in length. Unless fertile tissue was involved all blade tissue, except that closely adjoining the bulb, became thinner during growth. R in volume reached 0.3 day⁻¹. Presumably because the plants were held near the sea surface stipes grew slowly, with a maximum linear rate of 9 mm day⁻¹. The maximum R in length decreased with stipe length. Bulb R in volume also decreased as size increased, from a maximum of 0.3 day⁻¹.     

A NEW SPECIES OF ENSICULIFERA,E. IMARIENSE (DINOPHYCEAE), PRODUCING ORGANIC-WALLED CYSTS1

We describe a new organic-walled resting cyst from surface sediments of Imari Bay in western Japan. The cysts are spherical, 23–29 pm in diameter, and their surface is covered with spinous to membranous ornaments that are 5–7 μm long and 1.5–2.2 μm wide. The ornaments vary from slender and bifurcate to membranous and multifurcate distal extremities. No archeopyle was observed. The cyst shape is variable in both natural samples and clonal cultures. Vegetative cells are small and ovoid, 17–25 μm long and 14–21 μm wide, and are yellow-brown in color. The epitheca is conical with a conspicuous apical horn, and the hypotheca is hemispherical. The cingular transitional plate has a needle-like spine at its anterior right corner. The plate formula is Po, X, 4″3a, 7″, 5c, 5s 5″and 2″. Although vegetative cells of the present species correspond to Ensiculifera, it is distinct from other species in producing no calcareous cysts. No species of Ensiculifera has been reported to produce cysts composed of only an organic wall. The present species is provisionally placed in the genus Ensiculifera as E. imariense sp. nov.