University Herbarium, UC Berkeley

CENTER FOR PHYCOLOGICAL DOCUMENTATION
DECEW'S GUIDE

KEY TO GENERA AND SPECIES OF BROWN ALGAE

CONTENTS  |  FIGURES  |  ABOUT  |  INDEXES: Reds · Greens · Browns  |  KEYS: Browns

1 Thallus appears filamentous 2
  1 Thallus other than a simple filament 23
< 2 Thallus wholly or partly endophytic 3
  2 Thallus free-living or epiphytic 6
< 3 Branching at right angles; multiseriate at maturity; host the epiphytic red alga Smithora Internoretia fryeana
  3 Branching at oblique angles; uniseriate throughout 4
< 4 Lifting the surface of Hedophyllum, often erupting through the epidermis Gononema aecidioides
  4 Filaments among the bases of the unangia in other laminarians 5
< 5 Host is Laminaria setchellii Streblonema evagatum
  5 Host is Alaria Streblonema pacificum
< 6 Thallus multiseriate and parenchymatous in part, though appearing filamentous 7
  6 Thallus truly filamentous in structure 8
< 7 Multseriate thallus behind a large and distinctive apical cell Sphacelaria (see genus key)
  7 Multiseriate thallus behind an intercalary meristem that produces a uniseriate terminal filament Stictyosiphon tortilis
< 8 Hooked branchlets unite upright branches in yarn-like strands, on fucoids Spongonema tomentosum
  8 Branches generally free or absent 9
< 9 Reproductive organs intercalary 10
  9 Reproductive organs not intercalary 13
< 10 Minute epiphyte on Postelsia stipes; plurangia in axes and in paired, opposite branches Pilayella gardneri
  10 On various substrates; organs in catenate series 11
< 11 Unbranched 12
  11 Branched Pilayella littoralis
< 12 Reproductive organs large and globose, not in adjacent series Leptonematella fasciculata
  12 Unangia in series below series of plurangia, to the tip of the filament Pilayella tenella
< 13 Minute, epiphyte on Fucus, unangia borne laterally near filament base Elachista fucicola
  13 On various substrates, plurangia common 14
< 14 Discoid base 15
  14 Filaments attached at the base by rhizoids or a short prostrate filament 19
< 15 Basal disc distromatic in part 16
  15 Basal disc monostromatic 17
< 16 Small (<2mm) discs on the blades of laminarians Hecatonema primarium
  16 Circular or irregular cushions (to 10 mm), often confluent Hecatonema streblonematoides
< 17 Short unbranched or sparingly branched uprights. Myrionema (see genus key)
  17 Dense mat of unbranched upright filaments 18
< 18 Erect filaments 10 - 12Ám in diameter, on Nereocystis Compsonema serpens
  18 Erect filaments 8 - 9Ám in diameter, on large algae Compsonema fructuosum
< 19 Meristem at the base of branches, above which no lateral branching occurs 22
  19 Meristem inconspicuous and diffuse 20
< 20 Plurangia on short lateral branches, growth intercalary Ectocarpus (see genus key)
  20 Plurangia sessile, generally asymmetrical, meristems inconspicuous 21
< 21 Plurangia arranged in unilateral series on axes Hincksia sandriana
  21 Plurangia irregularly arranged, mostly singly Hincksia granulosa
< 22 Plurangia irregularly conical, tapering sharply to tip Feldmannia irregularis
  22 Plurangia cylindrical, thin, and blunt tipped Feldmannia simplex
< 23 Thallus robust and evidently parenchymatous 24
  23 Thallus appears cylindrical, globose, saccate, or crustose 57
< 24 Thallus with distinct blades and hapteran holdfast separated by a stipe 25
  24 Thallus parenchymatous or pseudparenchymatous, stipe insubstantial or absent 44
< 25 Thallus with differentiated sporophylls and vegetative blades 26
  25 Thallus in which all blades are sporophyllous or which bear conceptacles 31
< 26 Sporophylls borne laterally on stipe, below a single vegetative blade 27
  26 Sporophylls borne otherwise 28
< 27 Teminal blade with conspicuous midrib, lamina thin, stipe flexible Alaria (see genus key)
  27 Terminal blades smooth, lamina tough and leathery, stipe stiff and woody Pterygophora californica
< 28 Blades formed in terminal dichotomies, without pneumatocysts Lessoniopsis littoralis
  28 Blades with basal pneumatocysts formed laterally 29
< 29 Sporophylls and vegetative blades profuse along a flattened rachis Egregia menziesii
  29 Blades regularly spaced on long, cylindrical branches 30
< 30 Blades and pneumatocysts small and densely packed Sargassum muticum
  30 Blades and pneumatocysts large and well spaced Macrocystis integrifolia
< 31 Stipe prostrate with haptera growing from sides 32
  31 Stipe upright 33
< 32 Blades branching by splitting from the base to the tip; no midrib Dictyoneurum californicum
  32 Blades unbranched; distinct midrib Dictyoneuropsis reticulata
< 33 Stipe branched 34
  33 Stipe unbranched, terete or flat but not blade-like 36
< 34 Stipe flattened near base; seasonally terete near tip, bearing pneumatocysts and conceptacles 35
  34 Stipe appears dichotomously and repeatedly branched near tip Eisenia arborea
< 35 Pneumatocysts in catenate series Cystoseira osmundacea
  35 Pneumatocysts in pairs Cystoseira geminata
< 36 Blades with one or more midribs 37
  36 Blades without a percurrent rib 41
< 37 Blades with multiple percurrent midribs, bullations common 38
  37 Blade with a single midrib 39
< 38 Blade with five longitudinal ribs Costaria costata
  38 Blade with three longitudinal ribs Cymathere triplicata
< 39 Blade about as wide as long, bullate, frequently perforated 40
  39 Blade longer than wide, bullations along midrib Pleurophycus gardneri
< 40 Stipe cylindrical, not fimbriate; blade with two basal scrolls Agarum fimbriatum
  40 Stipe flattened, with fimbriate margins; blade base rounded or cordate Agarum clathratum
< 41 Blades smooth, without notable bullations, ridges, or perforations Laminaria (see genus key)
  41 Blades ornamented with bullations, ridges, or perforations 42
< 42 Stipe solid topped with a single blade Laminaria (see genus key)
  42 Stipe hollow, several ridged blades 43
< 43 Stipe terminates in a bulbous pneumatocyst and numerous lamina Nereocystis luetkeana
  43 Stipe narrows towards the tip and lamina Postelsia palmaeformis
< 44 Thallus a thin blade 53
  44 Thallus coarse and strong 45
< 45 Thallus a broad blade (frequently with falcate splits), haptera arise from blade edge Hedophyllum sessile
  45 Thallus other 46
< 46 Thallus roughly terete 47
  46 Thallus strap-like, dichotomously branched; discoid holdfast 49
< 47 Thallus unbranched or pinnately branched; strong discoid holdfast; acidulous Desmarestia (see genus key)
  47 With numerous irregular branches 48
< 48 Arising from crustose base; branches straight or tapering Analipus japonicus
  48 Small discoid holdfast; some branches clavate and blunt Saundersella simplex
< 49 Thallus with a midrib and well defined terminal receptacles 50
  49 Thallus narrow, without evident midrib; receptacles poorly defined 52
< 50 Thallus with pits in parallel rows along the midrib Hesperophycus californicus
  50 Thallus without rows of pits 51
< 51 Midrib and oval conceptacle sharply defined from blade Fucus spiralis
  51 Midrib and elongated conceptacle grade into blade Fucus gardneri
< 52 Dichotomies often unequal; two eggs in each oogonium Silvetia compressa
  52 Dichotomies generally equal; one egg and a polar body in each oogonium Pelvetiopsis limitata
< 53 Thallus epiphytic 58
  53 Growing on rocks, shells, or other inanimate substrate 54
< 54 Thallus a branched cylinder, extremely lax, lubricous, and covered with fine hairs Haplogloia andersonii
  54 Thallus other 55
< 55 Thallus flattened 56
  55 Thallus tubular, irregular, globose, saccate, or crustose 61
< 56 Blade fan-like, splitting into more narrow blades; thallus less than five cm high Syringoderma abyssicola
  56 Blade not fan-like, edges irregular or roughly parallel 57
< 57 Blade shape very irregular; growth from a perennial basal crust Phaeostrophion irregulare
  57 Blades mildly flabellate but not fan-like; to twenty cm or more when mature Dictyota binghamiae
< 58 Thallus epiphytic on Egregia Halorhipis winstonii
  58 Thallus epiphytic on sea grasses, occasionally on algae other than Egregia 59
< 59 Medullary cells four to five times the diameter of cortical cells Petalonia fascia
  59 Medullary cells two to three times the diameter of cortical cells 60
< 60 Thalli to 2.5 cm; margins plane Punctaria hesperia
  60 Thalli to 20 cm; margins ruffled Punctaria occidentalis
< 61 Thallus hollow 62
  61 Thalli crustose, not hollow 70
< 62 Thalli hollow but not distinctly tubular 65
  62 Clumps of tubular thalli found in high intertidal pools 63
< 63 Mature branches with spiral grooves creating a coiled appearance Melanosiphon intestinalis
  63 Mature branches not spirally grooved 64
< 64 Mature branches with regular constrictions; senescent blades up to one cm wide Scytosiphon lomentaria
  64 Mature branches without regular constrictions; seldom more than 0.4 cm wide Scytosiphon dotyi
< 65 Irregular, sub-spherical, or globose forms 68
  65 Thalli saccate 66
< 66 Sori numerous and distinct; epiphytic solely on the red algae Neorhodomela and Odonthalia Soranthera ulvoidea
  66 Sori not obvious; on rocks or epiphytic 67
< 67 Epiphytic on Cystoseira and other brown algae Coilodesme californica
  67 On rocks in the low intertidal and subtidal Coilodesme bulligera
< 68 Convoluted, globose forms; epiphytic, but often appearing saxicolous; smears when crushed Leathesia difformis
  68 Sacs with thin but strong walls that tear but do not crush 69
< 69 Dimpled, sub-spherical sacs, commonly epiphytic Colpomenia peregrina
  69 Finger like sacs, appear saxicolous but often epiphytic on crustose algae Colpomenia bullosa
< 70 Crust pulvinate, rugose, and spongy; frequently spreading Petrospongium rugosum
  70 Crust smooth and firm 71
< 71 Crustose thallus composed of tightly adherent upright filaments Ralfsia (see genus key)
  71 Crustose thallus composed of packed but not adherent filaments Petroderma maculiforme

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