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PDF file (text) - Cryptogamic Botany Company

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188<br />

THE MARINE ALGÆ OF NEW ENGLAND.<br />

Sporangia at the base of filaments, which form scattered external tufts Stilophora.<br />

38. Fronds minute, ending in a hyaline hair, monosiphonous below, densely beset above<br />

with very short branches, between which are the sporangia Myriotrichia.<br />

Fronds ending in a large, single cell, the cells of the lower part giving off descending<br />

filaments, which become interwoven and form a false cortex . 39<br />

39. Rhizoidal filaments few and limited to the base of the plant, branching, irregularly<br />

pinnate ...................................................................... Sphacelaria.<br />

Rhizoidal filaments numerous ........................................................ 40<br />

40. Branches distichously pinnate ................................. Chætopteris.<br />

Branches whorled ......................................................... Cladostephus.<br />

41. Fronds simple or occasionally proliferous ................................ 42<br />

Fronds branching ............................................................................. 47<br />

42. Midrib present ........................................................................... 43<br />

Midrib wanting ................................................................................ 44<br />

43. Fronds stipitate, perforated with numerous holes ........ Agarum.<br />

Fronds entire, with a few separate leaflets on the stipe below the lamina Alaria.<br />

44. Fronds thin, subsessile .............................................................. 45<br />

Fronds thick and coriaceous, distinctly stipitate ........................... 46<br />

45. Sporangia densely covering the surface of frond ........... Phyllitis.<br />

Sporangia external in scattered spots ........................... Punctaria.<br />

46. Cryptostomata present, fronds attached by short, nearly simple rhizoids<br />

Saccorhiza.<br />

Cryptostomata wanting, fronds attached by prominent, branching rhizoids<br />

Laminaria.<br />

47. Fronds without distinction of midrib and lamina, fruit borne on short lateral<br />

branches ................................................................... Ascophyllum.<br />

Blade distinct from the midrib, bladders borne in the laminae, fruit terminal Fucus.<br />

Bladders and fruit borne on special stalks ..................... Sargassum.<br />

48. Fronds calcareous ...................................................................... 49<br />

Fronds not calcareous ...................................................................... 50<br />

49. Fronds erect, filiform, articulated ................................ Corallina.<br />

Fronds thin, horizontally expanded .................................. Melobesia.<br />

Fronds thick, horizontally expanded, but rising at intervals in irregular protuberances<br />

Lithothamnion.<br />

50. Fronds horizontally expanded, crustaceous or membranaceous51<br />

Fronds erect or umbilicate .............................................................. 52<br />

51. Fronds parenchymatous, spores in external warts Peyssonnelia.<br />

Fronds parenchymatous, spores in cavities sunk in the<br />

frond .......................................................................... Hildenbrandtia.

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