File:Text-book of structural and physiological botany (1877) (14589934389).jpg

Identifier: textbookofstruct00thom (find matches)
Title: Text-book of structural and physiological botany
Year: 1877 (1870s)
Authors: Thomé, Otto Wilhelm, 1840- Bennett, Alfred William, 1833-1902
Subjects: Plant physiology
Publisher: New York : J. Wiley & sons
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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man ; and it is still an undecided question whetherthese cube-shaped cells united together in strings are ofpathological character or not. The number of types includedin Algae is not remarkably large ; but that of the individualswhich are collected in masses is enormously great. The gelatinous substance of the cell-walls gives toseveral kinds of Algae the property of being used as articlesof diet, such as the species of Laminaria and Ulva (greenlaver) on the coasts of Scotland and Ireland, and the ^ carra-geen moss which is obtained from Sphcerococcus crispus andmammillosiis. The ashes of the larger mg^rine Algae were atone time largely employed, as kelp, in the manufacture of special Morphology and Classification, 255 alkali, and still are for that of iodine. Gigarthina helmiu-thochortos furnishes worm-moss/ but is usually adulteratedwith other species of marine Algae. It cannot be said that there is at present any classifica-tion of Algae on a truly scientific basis. In its place a
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Fig. 387.—The gulf-weed, Sargassiwt natans, with globular berry-like swimming-bladders (natural size). selection may be made of typical forms, round which therest group themselves. The NosTOCACE/E form filiform unbranched rows of cells. Thefilaments are free in Oscillatoida ; while in Nostoc they are enclosed ingelatinous envelopes, and by the melting of these are often united intolarger colonies. The vegetative cells, which are capable of dividinginto daughter-cells, contain a homogeneous or granular protoplasm of a 256 Structural and Physiological Botany, bluish-green colour, caused by the mixture of the colouring matter ofchlorophyll with a blue and yellow pigment. The form of the in-dividual cells is discoid or nearly spherical. But little is known oftheir mode of reproduction. The HYDRODiCTYEiE contain pure chlorophyll, and are distin-guished by producing a large number of swarmspores which, aftercoming to rest, unite into a family. This is of tabular form in Pedias-trum (Fig.

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