. Botany for agricultural students. Plants. LAM IN ARIAS 319 plant body coniinonly consists of a stalk bearing leaf-like branches and attached to a support by root-like holdfasts. One might think such a plant too complex to be classed as a Thallophyte, for, according to definition, a Thallophyte is a plant not differen- tiated into roots, stem, and leaves. However, when the struc- ture of these parts that so much resemble roots, stems, and leaves is studied, one finds that they are too simple in structure to be classed as such organs, although they mark a notable advance- ment over the Green A
. Botany for agricultural students. Plants. LAM IN ARIAS 319 plant body coniinonly consists of a stalk bearing leaf-like branches and attached to a support by root-like holdfasts. One might think such a plant too complex to be classed as a Thallophyte, for, according to definition, a Thallophyte is a plant not differen- tiated into roots, stem, and leaves. However, when the struc- ture of these parts that so much resemble roots, stems, and leaves is studied, one finds that they are too simple in structure to be classed as such organs, although they mark a notable advance- ment over the Green Algae in the differentiation of the plant body. Some have special swollen regions called air bladders, which help. Fig. 274. — One of the Brown Algae, Macrocystis, showing the root-Uke hoklfasts, the stem-like axis, and the leaf-Uke blades. Much reduced. Re- drawn with modifications from Harvey. the plant to float, and in connection with reproduction there is much differentiation shown by some forms. There are about 1000 species of Brown Algae known and these are divided into two groups, one of which comprises the Kelps and closely related forms, and the other, the Rockweeds and Gulf- weeds. Kelps and Closely Related Forms (Phaeosporales). — This order comprises a number of families of which tlie Laminarias or Kelps are the largest forms. Laminarias. — These are the largest of Algae, and include such conspicuous forms as Nereocystis, Postelsia, or Sea Palm, and the huge Macrocystis (Fig. 274), which is sometimes more than 200 feet in length. It is from the massive plant bodies of the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Martin, John N. (John Nathan), b. 1875. New York, John Wiley ; London, Chapman & Hall
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